GB2073666A

GB2073666A - Printing press dampener system

Info

Publication number: GB2073666A
Application number: GB8109621A
Authority: GB
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1980-04-14
Filing date: 1981-03-27
Publication date: 1981-10-21
Also published as: FR2480183A1; JPS56157359A; SE8102358L

Abstract

A spray dampening system for web fed lithographic presses in which there is provided elongated manifold means 10 for conducting a supply of air and damping fluid to a plurality of individual nozzle means 13 located across the width of the printing couple and which also includes means to supply dampening fluid to the elongated manifold means 10 whereby the volume of fluid supplied can be regulated as a function of the number of individual nozzles that are in operation. The volume of fluid supplied may also be regulated by means 35, 36, 37 responsive to press speed. The fluid is preferably supplied by a pump 31 whose displacement can be varied to effect the regulation. <IMAGE>

Description

SPECIFICATION Press dampener system Background of the Invention The lithographic process for printing utilizes an image carrier that is essentially planographic, that is, the image area on the printing plate is essentially on the same plane as the non-image area. Thus, lithdgraphy differs from the well known relief processes where the printing areas stand in a totally different plane from the nonimage areas. Since the image carriers or plates are planographic, success of the lithographic process depends upon the use of plates that have been treated so that the image areas are hydrophobic, or not receptive to water, and the non-image areas are hydrophylic, which means that they are receptive to water.Since successful lithographic printing relies upon the presence of water to preclude the non-image areas from acquiring ink, it is apparent that fluid dampening of the print cylinder is an essential element to successful performance of the printing function.

In the past, the most common means for applying water to lithographic plate cylinders involved the use of water fountains, a vibrating distributor roller and a plurality of form rollers that transferred the fluid dampening medium from the vibrator roll to the plate. While the non-image areas have been characterized as hydrophylic and receptive to water, it will be understood that frequently minor amounts of agents are added to the water for a variety of purposes so that in a technical sense, the dampening medium does not always consist solely of water. As print quality and printing speed demands on modern web-fed rotary presses have increased, the need fqr improved dampener performance has been experienced. This invention provides positive, accurate, and reliable control of dampening fluid application.

A principal object of this invention is to provide an improved spray dampening system wherein the volume of fluid dispensed is accurately controlled under all conditions of press operation.

Another object of this invention is to provide an improved spray dampening system wherein the volume of fluid dispensed can be varied in accordance with the number of fluid outlets that are in operation across a printing couple.

Another object of this invention is to provide an improved spray dampening system which utilizes a valveless, piston type metering pump to vary the volume of fluid output to the spraying nozzles in the couple. This type pump is not subject to malfunction in pumping action due to air entrainment.

A further object of this invention is to provide an improved spray dampening system in which the flow of fluid per fluid outlet is rendered uniform.

Additional objects and advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawings in which; Brief Description of the Drawings Fig. 1 is a diagrammatic view showing the improved fluid dampening system of this invention; Fig. 2 is a schematic side elevation showing the plate roll and portion of the ink and dampening fluid supply system; and Fig. 3 is a side elevation showing one of the spray heads for applying dampening fluid to the fluid roll.

Description of the Preferred Embodiment It is well known that in today's high speed rotary offset presses, the small volume of dampening fluid supplied to the image carriers or plates must be accurately controlled at all press speeds. This small flow must also be equally divided across the image carriers or plates. Also, a plurality of image carriers or plates are frequently used across the width of a given printing couple.

However, even though the given printing couple may have the capability for printing several pages across its width, the total number is not always used in any given printing situation. For this reason it is frequently desirable to eliminate or shut down the application of dampening fluid to one or more sections of the printing couple.

However, it remain important that the quantity of water supplied to those portions of the press that are operating remain of constant volume at a carefully controlled'rate of application. The present invention makes possible accurate control of fluid application -either at maximum press capacity or at some lesser level of utilization.

The overall dampening system can best be seen by referring to Fig. 1 of the drawings where numeral 10 indicates an elongated manifold which has separate passages 11 and 1 2 for the flow of air and of dampening fluid respectively.

The manifold means 10 also includes a plurality of individual nozzles 13, shown schematically in Fig. 1.

Nozzles 13 are shown in more detail in Fig. 3 where one such nozzle is shown mounted to press frame member 14 by means of bolts 1 5 extending through a mounting adjustment plate 16. Thebody of the nozzle is made up of the manifold 1 0 and has an outlet orifice 20 and a control knob 21.

The control knob includes a small projection 22 that can be engaged with latch means 23. Each of the orifices can be closed by pushing knob 21 toward the manifold 10 and latching projection 22 within the latch means 23. The precise manifold construction as well as the construction of the nozzle can understood by referring to applicant's co-pending application No. 8109041 (Docket 3851 ) filed on even date herewith and assigned to the same assignee of the present invention.

Referring again to Fig. 1, air is supplied to air passage 11 by means of a compressor 25. The amount of air introduced into passage 11. can be controlled by any suitable sort of regulating means.

The dampening fluid or water is introduced into manifold passage 12 from a source of water 30.

From the source 30 the fluid is moved by means of a metering pump 31 that is valveless and which utilizes a ducted piston which reciprocates and rotates in a cylinder. This type of pump passes entrained gas and provides extremely reliable pumping action which cannot be matched with a small volume pump using spring loaded inlet and outlet valves. This one pump 31 supplies all of the dampening fluid to the fluid outlets 20,which may vary from 4 to 60 across a printing couple.

Since the volume of fluid required will vary with - the number of spray heads in operation and also with press speed, the present system includes a press foliower drive 35, speed potentiometer 36 and a variable speed motor 37. Use of elements 35 through 37 will result in the ability for pump 31 to vary in speed and thus to vary the output of dampening fluid to manifold 10. An important feature of the pump 31 is that of providing an adjustment in the throw or displacement of the piston contained therein. If the entire printing couple is being utilized and the maximum number of fluid dispensing heads are in operation, then the setting on the pump would be as shown. in Fig. 1 where it is placed on the number 4.The pump 31 is set up for application to a four-wide press and so if one quarter of the width of the press were not to be utilized, then the adjustment to the pump would be to move the indicator to number 3 to decrease the piston displacement. Such an adjustment would decrease the quantity of dampening fluid flowing to the manifold and would thereby maintain uniform flow at each of the fluid outlets.

Referring to Fig. 3,. numeral' 40 indicates the plate roll-and in contact with this roll are two ink form rollers 41 and an ink transfer roll 42. The spray head 13 is shown as directed against fluid transfer roll 45 which in turn imparts its fluid to the fluid form roller 46 that passes the film onto plate cylinder 40. By use of the adjustable throw pump in the fluid spray system, it is possible to vary the quantity of fluid to the spray manifold 10 as a function of the number of nozzle means that are in operation.

Although the present invention has been described in connection with a preferred embodiment, it is-to be understood that other modifications and variations may be resorted to without departing from the spirit and scope of the invention as those-skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.

Claims

1. In a spray dampening system for supplying dampening fluid to the plate cylinder of a web fed rotary printing press: (a) elongated manifold means including separate passages for the flow of air and of dampening fluid; (b) a plurality of individual nozzle means mounted in said elongated manifold means whereby atomized dampening fluid can be - controllably introduced for transport to the plate cylinder; (c) means to supply air under pressure to the air passage of said elongated manifold means to provide for atomization of the dampening fluid;and (d) means to supply dampening fluid under pressure to the fluid passage of said elongated manifold means, said fluid supply means including regulating means whereby the volume of fluid supplied to said manifold can be controlled as a function of the number of said nozzle means that are open for operation.

2. A dampening system as defined in claim 1 wherein said dampening fluid supply means includes control means responsive to press speed whereby the operating speed of said regulating means will vary as a function of press speed.

3. A dampening system as in claim 1 or 2 wherein the metering pump piston is ducted and rotates as well as reciprocating in a cylinder.

3. A dampening system as defined in claim 1 wherein said dampening fluid supply means includes a fluid metering pump having a piston whose~displacement can be varied to control the volume of fluid being introduced into said elongated manifold means.

4. A dampening system as defined in claim 2 wherein said dampening fluid supply means includes a precision metering pump whose output volume can be varied as a function of the number of said nozzle means in operating condition.

5. A dampening system as defined in claim 2 wherein said dampening fluid supply means includes a metering pump that is valveless and which utilizes a ducted piston which reciprocates and rotates in a cylinder

6. A spray dampening system for a rotary printing press substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

7. A printing press including a dampening system as in any one preceding claim.

New claims or amendments to claims filed on 24th July 1981 Superseded claims 1, 2, 3, 4, 5 New or amended claims:--

1. A spray dampening system for suppiying a flow of air contained dampening fluid to the plate cylinder of a-web fed rotary printing press including:: (a) elongated manifold meansdefining separate air and dampening fluid passages for the flow of air and of dampening fluid; (b) a plurality of individual nozzle means for spraying dampening fluid on the plate cylinder mounted in said elongated manifold means each of said nozzle means having open and closed positions whereby atomized dampening fluid can be controllably introduced for transport to the plate cylinder; (c) means to supply dampening fluid under pressure to the air passage of said elongated manifold means to provide for atomizarion of the dampening fluid; and (d) means to supply dampening fluid under pressure to the dampening fluid passage of said elongated manifold means, said fluid supply means including a valveless metering pump having a reciprocating piston and regulating means whereby the volume of fluid supplied to said manifold can be controlled as a function of the number of said nozzle means that are open for operation.

2. A dampening system as defined in claim 1 wherein said dampening fluid supply means includes control means responsive to press speed whereby the speed of said regulating means will vary as a function of press speed.