US3911815A

US3911815A - Mechanism for dampening the printing plate of an offset printing press

Info

Publication number: US3911815A
Application number: US512464A
Authority: US
Inventors: Hartwig Banfer
Original assignee: Roland Offsetmaschinenfabrik Faber and Schleicher AG
Current assignee: Roland Offsetmaschinenfabrik Faber and Schleicher AG
Priority date: 1972-05-02
Filing date: 1974-10-07
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14

Abstract

A dampening mechanism for feeding a film of water to the terminal ink form roller of a lithographic printing press, the water feed path including a resiliently surfaced fountain roller, a hard surfaced hydrophilic water feed roller and a resiliently surfaced transfer roller, the latter being positively driven at press speed and in contact with the ink form roller. Means are provided for separately driving the water feed roller at a variable speed in order to provide a variable amount of slip between the water feed roller and the transfer roller, thereby to control the rate of water feed to the form roller. In the preferred embodiment the form roller and transfer roller are both journaled in a subframe which is rockable about the axis of the ink feed roller between an active position and a retracted position for silencing water feed. Also in the preferred embodiment the ink feed roller is driven directly from the plate cylinder and auxiliary gearing is provided on the subframe for driving the transfer roller at press speed from the ink feed roller so that the transfer roller continues to rotate even in the water-silenced condition.

Description

United States Patent 11 1 1111 3,911,815

Banter Oct. 14, 1975 MECHANISM FOR DAMPENING THE 3,508,489 4/1970 Norton 101/148 PRINTING PLATE OF AN OFFSET 3,673,959 7/1972 .lezuit.... 101/148 NTIN 3,688,694 9 1972 Preuss... 101/148 PR1 G PRESS 3,715,979 2 1973 Erb 101/148 [75] Inventor: 'Hartwig Banfer, Wiesbaden,

Germany [73] Assignee: Roland Offsetmaschinenfabrik Faber & Schleicher AG, Germany [22] Filed: Oct. 7, 1974 [21] Appl. No.: 512,464

Related US. Application Data [63] Continuation of Ser. No. 355,447, April 30, 1973,

abandoned.

[30] Foreign Application Priority Data May 2, 1972 Gennany 2221423 [52] US. Cl 101/148; 101/350 [51] Int. Cl. B41F 31/14; B41F 7/26; B41F 7/32 [58] Field of Search -101/148, 349, 350, 351, 101/352 5 6] References Cited UNITED STATES PATENTS 2,733,654 2/1956 Rogers 101/148 3,029,729 4/1962 Gericke 101/148 X 3,094,065 6/1963 Roberts lOl/l48 3,146,706 9/1964 Tonkin et a1. lOl/148 3,168,037 2/1965 Dahlgren lOl/l48 3,404,625 10/1968 White 101/148 3,433,155 3/1969 Norton 101/148 3,504,626 4/1970 Worthington 101/148 II l5 l4 ,1) 1

Primary Examiner.l. Reed Fisher Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[ ABSTRACT A dampening mechanism for feeding a film of water to the terminal ink form roller of a lithographic printing press, the water feed path including a resiliently surfaced fountain roller, a hard surfaced hydrophilic water feed roller and a resiliently surfaced transfer roller, the latter being positively driven at press speed and in contact with the ink form roller. Means are provided for separately driving the water feed roller at a variable speed in order to provide a variable amount of slip between the water feed roller and the transfer roller, thereby to control the rate of water feed to the form roller. In the preferred embodiment the form roller and transfer roller are both journaled in a subframe which is rockable about the axis of the ink feed roller between an active position and a retracted position for silencing water feed. Also in the preferred embodiment the ink feed roller is driven directly from the plate cylinder and auxiliary gearing is provided on the subframe for driving the transfer roller at press speed from the ink feed roller so that the transfer roller continues to rotate even in the water-silenced condition.

10 Claims, 2 Drawing Figures US. Patent Oct. 14, 1975 driving arrangements, it is difficult to predict results,

and improvements are often brought about by the process of discovery. Conventional water feed systems leave much to be desired and the search for a system meeting all of the diverse requirements is a continuing one. Conventional systems, for example, fail to operate consistently, are difficult to adjust, prone to flooding, and tend to react upon the form roller to produce streaks and imperfections in the image. Moreover, many conventional systems which utilize the same form roller, or rollers, to apply water and ink to the plate, tend to form an emulsion of ink and water which affects the quality of the printing. In prior efforts to solve such problems it has been necessary to resort to feed systems which are so complex and expensive as to be impractical.

It is, accordingly, an object of the present invention to provide an ink feed systemfor a lithographic press which is highly efficient and which achieves consistent high quality in the printed product but which is simple in construction and which may be easily adjusted and operated by the average pressman. It is a more specific object of the invention to provide a water feed system which feeds a film of water to an ink form roll but which minimizes emulsification of the ink and water and which may be operated without constant attention during long press runs. It is another specific object to provide a water feed system in which the rate of water feed is subject to precise control and in which the form roller is permitted to perform the forming function, rotating with freedom and optimum pressure against the plate surfaces at precisely press speed, so as to avoid the smearing and other effects which are caused, in a conventional press, by loading the form roller. It is another detailed object to provide a water feed system in which the water feed roller engages a resilient transfer roller which is ink receptive and which is driven at press speed to supply water to the form roller outside of the main ink feed path and without direct contact between the water feed roller and the form roller.

It is another object of the invention in one of its aspects to provide a rockable subframe for mounting the form roller and the associated transfer roller which permits the latter to be separated from the plate cylinder and water feed roller simultaneously for silencing the water flow but which are engaged sequentially when the subframe is restored to active position to insure that the form roller is both wetted and inked at the time that it touches the plate.

It is a general object of the invention to provide a water feed system which is reliable and effective but which is nevertheless simple and inexpensive to construct, adjust and maintain.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a diagram showing a water feed mechanism constructed and arranged in accordance with the present invention.

FIG. 2 is a fragmentary section, foreshortened, looking along the line 22 in FIG. 1.

While the invention has been described in connection with a preferred embodiment, it will be understood that I do not intend to be limited to the particular embodiment shown but intend, on the contrary, to cover the various alternative and equivalent forms of the invention which may be included within the spirit and scope of the appended claims.

Turning now to the drawing there is shown a portion of a plate cylinder 10 having a plate 11 mounted upon its periphery. For applying ink to the plate an ink feed system 12 is provided including an ink roller 13, a first form roller 14, a vibrated ink feed roller 15 and a second or terminal ink form roller 16 which, as will appear, serves to convey water as well as ink to the printing plate. For driving the ink feed roller 15 a gear 17 on the plate cylinder meshes with an idler gear 18 which in turn meshes with a gear 19 located at one end of the roller 15. For vibrating the ink feed roller endwise as it rotates, a suitable vibratory mechanism, diagrammatically indicated at V, is used which may, for example, correspond to that disclosed in prior U.S. Pat. No. 3,345,941.

In operation the ink roller 13 receivesan ink film from the usual ink fountain and set of intermediate ink rollers (not shown). Most of the ink transferred to the feed roller 15 is picked up by the first form roller 14 and is applied to the printing plate. Only a minor portion of the ink gets through to the terminal form roller 16. Endwise vibration of the ink feed roller 15 serves to smooth the ink film on both of the form rollers.

In accordance with the present invention, a dampening mechanism is provided for supplying a film of water to the form roller 16, such dampening mechanism including a resilient fountain roller, a water feed roller and resiliently surfaced transfer roller which engages the form roller, the transfer roller being driven at press speed and the feed roller being spearately driven at a variable speed to vary the rate at which water is fed. Thus, turning more specifically to the drawing, a resiliently surfaced fountain roller 20 in a fountain 21 bears against a water feed roller 22, the pressure between the two being adjustable by an eccentric adjusting mechanism 23 at each end (only one of which is shown) having respective adjusting handles 24. The surface 25 of the water feed roller 22 is preferably of a hard hydrophilic nature, for example, chromium plated upon steel. Bearing against the surface of the water feed roller is a transfer roller 30. This transfer roller has a surface 31 formed of rubber or other resilient ink receptive material which is, however, harder, i.e. stiffer, than the surfacing material on the ink form roller 16 which it engages. By making the resilient covering of the transfer roller 30 of stiffer material than that on the form roller the line of rolling engagement between the two rollers will tend to remain at a more constant radius than if materials of nominally the same stiffness, but subject to localized variations were employed. In a practical case the covering 31 of the transfer roller may have a durometer rating of 40 shore while the material with which the form roller is covered may have a durometer rating of 30 shore.

For the purpose of driving the transfer roller at press speed, a gear 32 is provided at the end of the transfer roller which meshes with an idler gear 33 which in turn meshes with gear 19 (see also lower portion of P16. 2). As previously stated, the gear 19 is driven by meshing with a gear 18 which in turn meshes with gear 17 on the plate cylinder.

Means are provided for varying the pressure between the transfer roller and the water feed roller and between the transfer roller and the form roller 16. This is accomplished by a double eccentric adjustment at each end of the transfer roller 30 consisting of an eccentric cam 34 having an adjusting handle 35 and surrounded by a second, or outer, eccentric cam 36 having an adjusting handle37. The form roller 16 is also adjustably mounted at each end by an eccentric cam 38 having an adjusting handle 39.

In accordance with one of the important aspects of the present invention the water feed roller 22 has a separate driving means for driving at a variable speed which differs from press speed so that a condition of slippage exists between the surface 25 of the feed roller and the surface 31 of the transfer roller, the rate of slippage being utilized to control the rate at which water is fed to the transfer roller. Thus in accordance with the invention, a separate drive motor is provided having a pulley 51 which is connected by a belt 52 to a pulley 53 on the feed roller; the speed of the motor, and hence the speed of the feed roller, is determined by a motor speed control 54, such speed control being of a type well known in the art.

Further in accordance with the invention the fountain roller is driven at a speed which may be 1:1 with the peripheral speed of the feed roller 22 but which is preferably coordinated with, and different from, the peripheral speed of the feed roller. For example, the fountain roller may be slightly underdriven by providing a gear 55 on the feed roller which meshes with a gear 56 on the fountain roller but having a pitch diameter which is offset, as shown, from the line of contact so that the fountain roller tends to rotate at a speed which is less than the peripheral speed of the feed roller but which is related to it in a predetermined ratio. Alternatively, a drive connection 57 may be interposed between the drive motor 50 and the fountain roller 20 to provide a predetermined but adjustable drive ratio. By operating the fountain roller 20 at a peripheral speed which is slower than the speed of the feed roller, and by operating the feed roller at a speed which is slower than the peripheral speed of the transfer roller, the total slippage can be divided into two components, with some of the slippage occurring at the fountain roller and some at the transfer roller. The effeet, in any event, is to produce a film of water which is fed to the transfer roller at a controlled and adjustable rate, a rate which is variably less than would obtain if both the fountain roller and feed roller operated at press speed. The separate driving of the feed roller at a predetermined, selected lower speed, enables water to be fed evenly at the precise rate required by the plates on the plate cylinder tending to reduce the likelihood of a flooding condition.

In accordance with a still further aspect of the invention the form roller 16 and transfer roller 30 are not fixedly journaled in the frame of the press but are, on the contrary, journaled in a subframe which is swingable about the axis of the ink feed roller 15. The subframe 60 is, in the present instance, made up of a pair of spaced frame plates 61, 62 rockable about the axis 63 of the feed roller 15. The idler gear 33 is journaled at 64 in the plate 61. The adjusting cams 36 and 38 are fitted in alined circular openings in the plates 61, 62.

By mounting the transfer roller 30 and form roller 16 in a swingable subframe, the form roller may be disengaged from the plate simultaneously with disengagement of the transfer roller from the feed roller 22. To swing the subframe from the illustrated active position to a retracted position, an actuator is provided having a piston 71 connected to a piston rod 72 which is pivoted at 73 to alined arms 74, 75 which are respectively secured to the plates 61, 62 of the subframe. When pressure is applied to the actuator to move the piston to the right, the subframe is rocked bodily in the clockwise direction to swing the rollers to the illustrated active positions in which the form roller 16 bears forcibly against the plate on the plate cylinder. An adjusting screw 76, which positions the actuator 70 with respect to the main frame of the press, determines the position of the form roller 16 and hence the bearing pressure between the form roller and the plate cylinder, the force being determined by the spring rate of the resilient surfacing material on the form roller. When the pressure condition is reversed, that is, when pressure fluid is supplied to the opposite end of the actuator 70, the piston rod moves to the left rocking the subframe counterclockwise and breaking contact both at the plate cylinder and at the surface 25 of the feed roller. This silences the feeding of water but it is to be noted that even when the subframe is retracted the ink roller 15, transfer roller 30, and the form roller 16 continue to rotate, the transfer roller being driven by the idler gear 33, and the form roller being driven by reason of surface contact with the transfer roller 30.

Preferably, and in accordance with one of the detailed aspects of the present invention, the geometry of the rollers is such that the transfer roller 30 lies approximately on a line which interconnects the axes of the ink feed roller 15 and the water feed roller 22. This causes tangential contact with roller 22 to occur as the transfer roller is swung into its active position, as contrasted with the abrupt radial contact between the form roller 16 and the plate cylinder. As a result, as the subframe is swung downwardly, light contact will occur first between the surface of the water feed roller 22 and the surface 31 of the transfer roller 30 so that water is fed from the feed roller to the transfer roller thereby wetting the rotating form roller 16 before the form roller comes into actual contact with the plate. Thus there is no possibility of a dry form roller engaging the plate upon resuming press operation.

It will be apparent that the above mechanism amply carries out the objects of the invention. The terminal form roller 16 not only serves to apply ink received from the ink feed roller 16 to the surface of the plate, but the form rolle r also serves to convey a film of water imparted to it by the transfer roller 30. The transfer roller tends to isolate the form roller from the remainder of the system so that it can perform its dual forming function without interference and quite independently of the remainder of the system. It will be noted that the form roller 16 is not positively driven and is thus free to assume the precise speed of the printing plate with which it is in rolling engagement without any tendency toward scuffing or smearing at the engaged surfaces.

No torque loading is applied to the form roller 16 by either the ink feed roller or the transfer roller 30 since both of these rollers are driven, through a train of gearing, at press speed, from a gear 17 on the plate cylinder.

While water is fed to form roller 16 which forms a part of the inking system, it is to be especially noted that the transfer roller lies outside of the ink feed path, most of the ink being conveyed to the plate by the first form roller 14. Moreover, it is to be noted that the water is applied to the terminal form roller 16 on the downstream side of the region of engagement between this form roller and the vibrated ink feed roller 15. As a result almost all of the water which is fed from the water feed roller to the transfer roller is immediately transferred to the surface of the plate so that it is not acted upon by the vibrated roller, thereby greatly reducing the tendency toward emulsification of the water and ink which occurs in conventional presses and which has a degrading effect upon the quality of the printing.

Because of the adjustable eccentrics which are interposed between the shaft of the form and transfer rollers and the subframe, and because of the adjustment of pressure between form roller 16 and the printing plate brought about by adjusting screw 76, the pressures existing along the path of water flow may be optimized. Moreover, by reason of the adjustment of the eccentrics 23 at the end of the fountain roller, the normal or bearing pressure between the fountain roller and the water feed roller may be varied to control water flow by a variable squeegee" effect. That is to say, the fountain roller 20, rotating counterclockwise, tends to pile up water at the right hand side of the nip, and the amount of water which is actually passed through the nip, and along the surface of the feed roller 22 depends upon the pressure which is exerted between the rollers. Variations in the feed of water longitudinally of the fountain roller may be controlled to some degree by differential adjustment of the eccentrics 23 at the ends of the roller but, if desired, means may be provided for imparting laterial skew to the fountain roller such as the double eccentrics used on the transfer roller.

The result is to produce a highly reliable and efficient dampening system which may be easily and precisely controlled and which, once set, is capable of operating consistently over long press runs.

While the term water has been used herein for the sake of convenience, it will be understood that this term includes not only water but also mixtures of water and various additives or, indeed, any type of dampening fluid which might be substituted for water. Also while the term fountain has been used it will be understood that this term is intended as a general term to include any source of water fed to the water feed roller. The term press speed, of course, refers to the peripheral speed of the plate or plates on the plate cylinder. The term associated as used herein applied to the second ink form roller implies that the latter is desirably outside of the primary ink feed path.

What is claimed is:

1. In a mechanism for dampening the plates on the plate cylinder of an offset printing press, the combination comprising means defining an ink feed path including an ink feed roller and an associated resiliently surfaced ink form roller, the latter being in rolling engagement with the plates, means defining a water feed path including a resiliently surfaced fountain roller, a hydrophilic hard surfaced water feed roller and a resiliently surfaced transfer roller,"the latter being in rolling engagement with the ink form'roller, means for driving the ink feed roller and transfer roller at press speed, means for driving the water feed roller at a variable peripheral speed which differs from press speed so that slippage takes place between the water feed roller and the transfer roller thereby to vary the rate of water feed to the transfer roller, means defining a separate subframe upon which the form roller and transfer roller are mounted and which is swingable about the axis of the ink feed roller from an active position to a retracted position for disengaging the form roller from the plates and for disengaging the transfer roller from the water feed roller to cut off further feeding of water.

2. The combination as claimed in claim 1 in which the resilient surface of the transfer roller is stiffer than the resilient surface on the form roller.

3. The combination as claimed in claim 1 in which the transfer roller has means for independent bodily adjustment with respect to both the form roller and water feed roller.

4. The combination as claimed in claim 1 in which means including a double acting actuator coupled to the subframe is provided for swinging the latter between the active position and the retracted position and in which the actuator has means for adjusting the active position thereby to vary the degree of force exerted by the form roller against the plates.

5. The combination as claimed in claim 1 in which the transfer roller in its active position lies substantially upon a line connecting the centers of the feed rollers so that when the subframe is swung from its retracted position to active position tangential contact occurs between the water feed roller and transfer roller to begin the feeding of water to the latter and to the form roller prior to the engagement of the form roller with the plates.

6. The combination as claimed in claim 1 in which the fountain roller has a direct drive connection with the water feed roller and includes means for relative eccentric adjustment with respect to the water feed roller for varying the bearing pressures between the rollers.

7. The combination as claimed in claim 1 in which the transfer roller and water feed roller both include means for relative eccentric adjustment with respect to the subframe for varying the bearing pressures between the engaged rollers.

8. In a mechanism for dampening the plates on the plate cylinder of an offset printing press, the combination comprising means defining an ink feed path including an ink feed roller and an associated ink form roller, the latter being resiliently surfaced and in rolling engagement with the plates, means defining a water feed path including a resiliently surfaced fountain roller, a hydrophilic hard surfaced feed roller and a resiliently surfaced transfer roller, the latter being in rolling engagement with the ink form roller, the resilient surface of the transfer roller being stiffer than the resilient surface of the ink form roller, means for driving the ink feed roller from the plate cylinder at press speed, means for driving the water feed roller at a variable peripheral speed which differs from press speed so that slippage takes place between the water feed roller and the transfer roller thereby to vary the rate of water feed to the transfer roller, means defining a separate subframe upon which the form roller and transfer roller are mounted and which is swingable about the axis of the ink feed roller for disengaging the form roller from the plates and for disengaging the transfer roller from the water feed roller to cut off further feeding of water, and means including an auxiliary idler gear on the subframe for coupling the transfer roller to the ink feed roller for driving of the transfer roller at press speed.

9. The combination as claimed in claim 8 in which the resilient surface of the transfer roller has a durometer rating of about 40 shore and the resilient surface of the ink form roller has a durometer rating of about 30 shore.

10. In a mechanism for dampening the plates on a plate cylinder of an offset printing press, the combination comprising means defining a primary ink feed path having a first form roller for feeding ink to the plates, a vibrated hard surfaced ink feed roller engaging the first form roller, a second form roller in rolling engagement with the plates and the ink feed roller and lying outside of the primary ink feed path, a water fountain having a resiliently surfaced fountain roller, a water feed roller having a hard hydrophilic surface running in engagement with the fountain roller, a resiliently surfaced transfer roller having an ink receptive surface interposed between the water feed roller and the second form roller, the surface of the transfer roller being stiffer than the surface of the second form roller, means for adjusting the pressure between the transfer roller and the second form roller and between the transfer roller and the water feed roller, means for separately driving the water feed roller and the fountain roller at a variable speed to provide variable slippage between the water feed roller and the transfer roller thereby to vary the rate of water feed to the second form roller, and means defining a separate sub-frame upon which the second form roller and transfer roller are mounted and which is swingable about the axis of the ink feed roller for disengaging the second form roller from the plates and for disengaging the transfer roller from the water feed roller to cut off further feeding of water.

Claims

1. In a mechanism for dampening the plates on the plate cylinder of an offset printing press, the combination comprising means defining an ink feed path including an ink feed roller and an associated resiliently surfaced ink form roller, the latter being in rolling engagement with the plates, means defining a water feed path including a resiliently surfaced fountain roller, a hydrophilic hard surfaced water feed roller and a resiliently surfaced transfer roller, the latter being in rolling engagement with the ink form roller, means for driving the ink feed roller and transfer roller at press speed, means for driving the water feed roller at a Variable peripheral speed which differs from press speed so that slippage takes place between the water feed roller and the transfer roller thereby to vary the rate of water feed to the transfer roller, means defining a separate sub-frame upon which the form roller and transfer roller are mounted and which is swingable about the axis of the ink feed roller from an active position to a retracted position for disengaging the form roller from the plates and for disengaging the transfer roller from the water feed roller to cut off further feeding of water.

8. In a mechanism for dampening the plates on the plate cylinder of an offset printing press, the combination comprising means defining an ink feed path including an ink feed roller and an associated ink form roller, the latter being resiliently surfaced and in rolling engagement with the plates, means defining a water feed path including a resiliently surfaced fountain roller, a hydrophilic hard surfaced feed roller and a resiliently surfaced transfer roller, the latter being in rolling engagement with the ink form roller, the resilient surface of the transfer roller being stiffer than the resilient surface of the ink form roller, means for driving the ink feed roller from the plate cylinder at press speed, means for driving the water feed roller at a variable peripheral speed which differs from press speed so that slippage takes place between the water feed roller and the transfer roller thereby to vary the rate of water feed to the transfer roller, means defining a separate sub-frame upon which the form roller and transfer roller are mounted and which is swingable about the axis of the ink feed roller for disengaging the form roller from the plates and for disengaging the transfer roller from the water feed roller to cut off further feeding of water, and means including an auxiliary idler gear on the sub-frame for coupling the transfer roller to the ink feed roller for driving of the transfer roller at press speed.