US2878502A

US2878502A - Dampening means for printing plates

Info

Publication number: US2878502A
Application number: US409728A
Authority: US
Inventors: Thomas H Johnson
Original assignee: Harris Intertype Corp
Current assignee: Harris Corp
Priority date: 1954-02-11
Filing date: 1954-02-11
Publication date: 1959-03-24
Anticipated expiration: 1976-03-24

Description

March 1959 T. H. JOHNSON DAMPENING MEANS FOR PRINTING PLATES Filed Feb. 11. 1954 2 Sheets-Sheet l INVENTOR. THOMAS H JOHNSON March 24, 1959 'r. JOHNSON 2,878,502

DAMPENING MEANS FOR PRINTING PLATES Filed Feb. 11, 1954 2 Sheets-Sheet 2 IN VEN TOR.

THOMAS H JOHNSON United States Patent DAMPENIN G MEANS FOR PRINTING PLATES Thomas H. Johnson, Peninsula, Ohio, assignor to Harris- Intertype Corporation, a corporation of Delaware Application February 11, 1954, Serial No. 409,728

Claims. (Cl. 15-183) 2,878,502 Patented Mar. 24, 1959 shaft 22. As shown, shaft 20 is frictionally driven in the clockwise direction as viewed in Fig. 1, while shaft 22 is also driven in a clockwise direction. Hence at their line of contact they are so turning that the movement of one opposes the movement of the other. The rotation of either or both of these shafts may be reversed. Shaft 22 is driven continuously by positive means at any suitable speed but preferably at the median speed of the pan roller 14. Preferably also means are provided, not sh0wn, for disconnecting the drive to shaft 22 so as to discontinue transmission of liquid to the vibrating roller terial to a rotating surface, such as a planographic printing plate mounted upon a cylinder.

Another object is the provision of a novel distributing roller having brush elements spirally located thereon so as to substantially eliminate stalling of a friction driven pan roller contacted thereby and turning in an opposing direction.

Another object is the provision of a distributing roller having brushes which are sectional longitudinally of the roller, each section being adapted to be readily disabled to control the amount of liquid applied to different portions of the plate.

Still another object is the provision of a plurality of identical brush holders disposed along the length of the brush shaft and each holder having a given number of brush elements evenly spaced around it, each holder being adapted to be clamped to the brush shaft at a selected angle with respect thereto, whereby a like number of spiral rows of brushes may be formed by the angular adjustment of said holders.

1 Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawings, in which Fig. 1 is a fragmental view partly in vertical section of means for dampening the plate on the plate cylinder of an offset printing machine;

Fig. 2 is a fragmental plan view on a larger scale; and

Figs. 3 and 4 are elevational views partly in section on the line 3-4 of Fig. 2, Fig. 3 showing all brush elements of a given brush holder in operative position and Fig. 4 showing two such elements retracted and inoperative.

A lithographic plate 10 mounted on the plate cylinder 11 of an offset printing press is illustrated in Fig. 1, the plate being contacted by a pair of dampening form rollers 12 of conventional character. They may be fabric covered rollers. A vibrating roller 13 having a metal surface preferably of aluminum bears against form rollers 12.

14 is a pan roller which is preferably made of brass plated with a water receptive chrome. It dips into water 15 or water containing certain chemicals, although the dampening liquid may be applied to the roller 14 by other means if desired. Roller 14 is rotatably driven by a suitable variable speed mechanism including a friction clutch 16. The speed of the roller may therefore be varied in relation to the press speed so that more or less water is transferred to the plate 10 as desired.

Pan roller 14 is mounted upon a shaft 20 and the distributing brush roller, herein numbered 21, is carried by the major portion and is split to form a shaft gripping means. On either side of the split this gripping portion of the sleeve includes two ears 25 through which a bolt 26 extends for clamping the holder to the shaft.

As shown in the drawings each holder carries four pairs of outwardly extending arms 27, the difierent pairs being spaced apart at ninety degree intervals. In each pair of these arms there is mounted a pivot pin 28 which is parallel to the shaft and upon which is mounted a brush carrier 29. Each carrier receives a brush element 30, the carrier being preferably provided with a slot into which the brush element may be slid and to which it may be secured against movement by any suitable means such for example as one or more setscrews 31, Fig. 2. It is to be understood of course that instead of four brush carriers for each holder 23, a lesser or greater number may be employed and evenly spaced around the shaft.

The brush holders 23 are so spaced along the shaft 22 that the brush elements 30 of one holder will approximately meet the brush elements of the next holder. However I prefer that the brush elements of adjacent holders shall overlap slightly relative to the length of the shaft so that distribution of the dampening liquid may be uniform and no streaking of the plate 10 will occur.

Each holder 23 is clamped to the shaft 22 at a slight angle to the adjacent holders on either side thereof, and thus several rows of brush elements are arranged spirally on the shaft 22, the number of rows corresponding to the number of brush elements on each holder. Consequently at any given time the contact between the distributing brush roller 21 and the pan roller 14 will be relatively small and any tendency which the constantly rotating distributing brush may have to stall the friction driven roller 14 will be inconsequential.

The amount of dampening liquid ideally to be applied to the plate 10 varies with the image variations along the length of the plate. In order to approximate such ideal conditions I provide means for disabling one or more brush elements on each holder. In Fig. 3 all brush elements of a given holder are in operative position, while in Fig. 4 two of them are operative and two are inoperative. For this purpose each brush carrier 29 may be rotated upon its pivot pin from its operative radial posi tion through ninety degrees to its inoperative tangential position. In order to hold each brush carrier in either position I provide a leaf spring retainer 35 which is secured to a flattened part of the holder 23 by a screw 36. Each retainer has an angular portion adapted to bear with pressure against either a side or the base surface of its corresponding brush carrier 29. The angular portion serves in conjunction with a lip 37 substantially as an over-center device to retain the brush carrier in its operative or inoperative position. The lip 37 serves also as an abutment for the carrier 29 against its holder 23 when the brush is in its operative position to limit pivotal movement of the brush and carrier in a direction opposite to the direction of rotation of the brush roller 21 when the brush contacts the pan roller 14. Because of the way in which the brushes are carried on the holder 23, the roller 21 may be adapted for counterclockwise rotation by removing all of the holders from the shaft 22 and turning them end for end. The spring retainers 35 are, of course, always on the side of their corresponding carriers opposite the direction of rotation. Movement of the individual carriers from operative to inoperative position and vice versa is accomplished as an easy manual adjustment by the machine operator without the use of tools.

The roller 21 may be so mounted as to be movable laterally toward either the vibrating roller 13 or the pan roller 14 or both to regulate the amount of water supplied to the plate by providing more or less contact between the brushes and those rollers.

Having thus described my invention, I claim:

1. In mechanism of the character described, a distributing roller comprising a shaft, a series of brush holders mounted on said shaft disposed along the length thereof, a brush element mounted on each holder, each of said elements having an operative substantially radial position and a retracted substantially tangential position, the base of each element being mounted to swing between said positions upon an axis parallel to said shaft, and resilient means carried by each of said holders for contacting one or the other of two different portions of the base of its corresponding brush element for selectively holding each element either in operative or in retracted position.

2. A distributing roller substantially as described in claim 1, wherein each of said bases has a side surface and a rear surface at right angles to each other substantially, and wherein said resilient means consists of a leaf spring attached to said holder at one end, the free end of said spring engaging the side of the base when the brush element is in radial position and engaging said rear surface when the element is in its tangential position.

3. A distributing roller for the purpose described comprising a shaft, a series of brush holders mounted on said shaft disposed along the length thereof, each of said holders comprising a split sleeve, means for contracting said sleeve into shaft gripping condition at any selected angle, each of said holders carrying a given number of pivot pins parallel to said shaft evenly spaced around the shaft, a brush carrier mounted to turn on each pivot pin, each of said holders benig clamped to said shaft at a predetermined angle with respect to the holders on either side thereof, a brush element mounted on each of said pins, whereby there is constituted a number of spiral rows of brushes equal to the number of brush elements on each holder, manually operable means for swinging one or more selected brush elements of any holder into retracted inoperative position, and means for retaining each brush element in its selected operative or inoperative position.

4. A distributing roller comprising a central shaft and a plurality of brush holders mounted on the shaft in juxtaposition progressively extending throughout the length of the shaft, a plurality of brushes carried by each holder, each brush being adapted to be selectively positioned either to extend outwardly into radial operative position or to be withdrawn into a tangential position completely within the field of action of the radial brushes, and means cooperating with each brush for retaining the brushes in the positions selected.

5. In mechanism of the character described, a distributing roller comprising a shaft, a series of brush holders mounted on said shaft disposed along the length thereof, a brush element mounted on each holder, each of said elements having an operative substantially radial I position and a retracted substantially tangential position, the base of each element being mounted to swing between said positions upon an axis parallel to said shaft, and means carried by each of said holders for holding the base of the corresponding brush element mounted thereon either in operative or in retracted position.

References Cited in the file of this patent UNITED STATES PATENTS 674,384 Nash May 21, 1901 843,222 Luther Feb. 5, 1907 2,194,577 Vonnegut Mar. 26, 1940 2,246,837 Carlson June 24, 1941 2,283,833 Troxler May 19,1942 2,496,010 Lotters Jan. 31, 1950 2,580,667 Faeber et al. Jan. 1, 1952 2,654,314 Southway -Q. Oct. 6, 1953