US3283712A

US3283712A - Wiper roll inking device for printing machines using fatty inks

Info

Publication number: US3283712A
Application number: US518045A
Authority: US
Inventors: Chambon Louis Jean
Original assignee: Societe dEtudes de Machines Speciales SA
Current assignee: Societe dEtudes de Machines Speciales SA
Priority date: 1962-09-21
Filing date: 1966-01-03
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08
Also published as: FR1341700A

Description

Nov. 8, 1966 L. J. CHAMBON WIPER ROLL INKING DEVICE FOR PRINTING MACHINES USING FATTY INKS 5 Sheets-Sheet 1 Filed Jan. 5, 1966 Nov. 8, 1966 L. J. CHAMBON 3,233,712

WIPER ROLL INKING DEVICE FOR PRINTING MACHINES USING FATTY INKS Filed Jan. 5, 1966 5 Sheets-Sheet 2 United States Patent 3,283,712 WIPER ROLL INKING DEVICE FOR PRINTING MACHINES USING FATTY INKS Louis Jean Chambon, Paris, France, assignor to Societe dEtudes de Machines Speciales, Paris, France Filed Jan. 3, 1966, Ser. No. 518,045 Claims priority, application France, Sept. 21, 1962, 910,165, Patent 1,341,700; Dec. 10, 1962, 918,075, Patent 1,341,700

1 Claim. (Cl. 101-350) This patent application is a continuation-in-part of my prior patent application Ser. No. 309,531 filed on September 17, 1963, now abandoned.

The present invention relates to a device for distributing a thin regular film of high-viscosity liquid on the surface of a cylinder or roller lined with or consisting of flexible material, this device being applicable notably to the inking of fatty-ink printing machines such as offset machines.

These printing machines comprise a roller lined with flexible material, called inking roller, receiving ink from an inking device and adapted to deposit said ink onto an etched portion of the printing cylinder or roller. The inked portions of the etching take a certain amount of ink from the ink film carried by the outer peripheral surface of the inking roller but no ink is taken by the nonetched or plain portions of the printing cylinder. Under these conditions, when the inking of said etched portions is completed the inking roller has inked residual surface portions called transfers.

Inking devices are already known wherein the residual ink transfers formed on the surface of the inking roller are blended into a mass of ink contained in the space overlying the line of mutual contact of said inking roller and ink feed roller, the thickness of the ink film deposited on the surface of the inking roller being adjusted by varying the pressure exerted on this roller by the ink feed roller.

However, these devices are always equipped with equalizing rollers tangent to the inking roller in the surface area of the inking roller which extends from the aforesaid line of mutual contact of said inking roller with the ink feed roller to the line of contact of said inking roller with the etched or printing cylinder.

It is one of the essential objects of the present invention to provide an improved device for inking the inking roller lined with flexible material in a fatty-ink printing machine, this device being characterized primarily by an extremely simplified structure.

It is another object of this invention to provide a device for inking the inking roller lined with flexible material in a fatty-ink printing machine, wherein the thickness of the ink film deposited on the peripheral surface of the inking roller can be controlled in a particularly simple manner without requiring the use of an equalizing roller.

Furthermore, this invention also contemplates the provision of a device for inking the inking roller lined with flexible material in a printing machine utilizing fatty ink, whereby a strictly constant ink-film thickness is obtained on the inking cylinder, throughout the length thereof.

This invention is based on the discovery, resulting from experimental works, that if for a given ratio of the velocities of rotation of the inking roller and ink feed roller, respectively, the pressure between the inking roller lined with flexible material and the ink feed roller of rigid material exceeds a certain critical threshold corresponding to a given compression of the lining of said inking roller, the thickness of the ink film deposited on the outer peripheral surface of said inking roller lined with flexible material will remain practically unchanged and attain a value corresponding substantially to a limit thickness. This is due to the fact that the flexible material lining the peripheral surface of the inking roller yields when the pressure value oversteps this threshold. Thus, if the pressure produced between the flexible surfaced inking roller and the rigid-surfaced ink feed roller is kept at a value in excess to said critical threshold,'the thickness of the resulting ink film spread throughout the length of the ink feed roller will be strictly constant and inferior or equal to the limit thickness corresponding to the threshold of critical pressure. An ink-film thickness inferior to said limit thickness may be obtained by adjusting accordingly the velocity of rotation of the ink feed roller having the complementary function of a wiper roller. In fact, the higher the velocity of rotation of this ink feed roller, the thinner the ink film carried by the peripheral flexible surface of the inking roller.

The inking device according to this invention is also characterized by a very important featureover hitherto known devices. In fact, since the inking roller lined with flexible material and the rigid-surfaced ink feed roller have a'certain length and the contact pressure is obtained by altering the relative positions of the ends of the shafts of these rollers, the local pressure at any selected point of the contact generatrix is not strictly constant throughout the length of these rollers as a consequence of their flexibility. It is thus clear that if it is desired to adjust the thickness of the ink film by simply adjusting the contact pressure between the two rollers, local pressure values that are not constant along the contact generatrix are obtained, thus causing detrimental inequalities in the thickness of the ink film on the surface of the inking roller.

On the other hand, in the inking device according to the present invention if the contact pressure between the two rollers is adjusted at a pressure value such that the local pressure at any point selected along the contact generatrix be always superior to the above-defined critical pressure threshold, the ink film spread on the peripheral.

surface of the inking roller has a reliably constant thickness throughout the length of this roller, this thickness being equal to or lower than the limit thickness. The actual value of this thickness is subordinate to the velocity of rotation of the inking roller which then acts as a wiper roller.

A typical form of embodiment of the present invention will now be described by way of example with reference to the attached drawings in which:

FIGURE 1 is a diagrammatic elevational view showing an inking device constructed according to the teachings of this invention.

FIGURE 2 is a developed diagram showing the surface of the inking roller of flexible material to illustrate the various operations carried out on this roller.

FIGURE 3 is a fragmentary view showing on a larger scale the contact zone between the inking and ink-feed rollers.

FIGURE 4 is a diagram illustrating the variation in the thickness of the ink fihn between the two rollers for a zero velocity of rotation of the ink feed roller, as a function of the sag resulting from the compression of the flexible material lining the inking roller.

FIGURE 5 is a diagram showing the equipment utilized for the experimental works having led to the present invention.

FIGURES 6, 7 and 8 are other diagrams illustrating the results of the tests made by utilizing the equipment shown in FIGURE 5.

In the following description reference will be made to an offset printing machine operating with fatty ink, but it will readily occur to anybody conversant with the art that this invention is applicable as well to any machine or device involving the distribution of a thin, regular film of high-viscosity liquid to the outer surface of a cylinder or roller lined with flexible material.

In FIGURE 1 there is illustrated an etched roller 1 of a printing machine which receives ink from an inking roller 2 lined with flexible material (plastic or rubber). An ink feed roller 3 (constituting in fact as a rule an ink distributor and wiper roller) is kept in contact with the inking roller 2 along a contact generatrix designated by the reference numeral 4.

Overlying this contact generatrix 4 is a mass or fountain of ink 5 filling the lower portion of the space bounded by the peripheral surfaces of these two rollers.

The etched cylinder 1 and inking roller 2 are rotatably mounted on a fixed frame structure 7, and the ink feed roller 3 is rotatably mounted on a support 8 fulcrumed on a shaft 9. A hydraulic cylinder 10 permits of adjusting at will the contact pressure between

rollers

2 and 3.

Rollers

1, 2 and 3 are rotatably driven in the direction shown by the corresponding arrows by means of

motors

11 and 19. The motor 11 drives the etched cylinder 1 and inking roller 2 by means of a train of gears 15, and motor 19-drives the ink feed roller 3 through the intermediary of another train of gears shown only diagrammatically at 16.

The inking roller 2 and ink feed roller 3 revolve in a clockwise direction; thus, their adjacent or contact surfaces move in opposite directions and under these conditions the ink feed roller 3 also acts as a wiper-with respect to the inking roller 2.

The reserve or fountain of ink 5 is retained by a doctor 12 engaging with its operative end the outer periphery of inking roller 3 above the contact generatrix 4.

Referring now to FIGURE 2 it will be seen that the relief or projecting portions 1a of etched cylinder 1 take a certain amount of ink from the ink film 6 coating the peripheral surface of inking roller 2, after the contact generatrix 4, and that no ink is taken therefrom by the hollow portions 1]) of said printing cylinder. As a result, ink-free zones 6a are formed in the ink film 6 which correspond to the inked portions 1a of etched cylinder 1, and other zones 6b are also formed wherein the ink thickness is unchanged and constitute what is commonly referred to as transfers. These ink tranfers 6b appearing on the outer surface of inking roller 2 after the transfer of ink to the etched cylinder 1a are fed to the mass of ink 5 and left therein. Thus, downstream of the contact generatrix 4 between the ink feed roller 3 and the inking roller 2, an ink film 6, of which the thickness is adjustable in a strictly constant and uniform manner by means of the present invention, is deposited on the inking roller 2.

The ink film thickness is adjusted by modifying two parameters, namely on the one hand the pressure existing in the nip 4 between the

rollers

2 and 3, and on the other hand the relative rotational speed of these two rollers. In fact, it was observed that in offset machines having an inking roller 2 lined with flexible material it is not possible to reduce the thickness of the ink film 6 carried by the surface of this inking roller 2 beyond a certain limit thickness even if the pressure between the ink feed roller 3 and inking roller 2 were increased considerably. The results of the theoretical study and also of the practical tests having confirmed the theoretical anticipations.

Referring now to FIGURE 3 it will be seen that the nondeformable ink-feed and wiper steel roller 3 having a radius R and the deformable inking roller 2 having a radius R and a rubber-lined surface revolve in the same direction; in other words, their adjacent surfaces move in opposite direction in the contact zone, respectively at speeds v (ink feed roller 3) and v, (inking roller 2).

Assuming that these

rollers

2 and 3 are pressed against each other, in the absence of the reserve of ink 5, it will be seen that the rubber lining of the inking roller 2 is squeezed to an extent or sag d depending on the pressure produced between the two rollers. If the ink 5 is fed into the pocket formed above the nip of these rollers an ink film having a thickness 11 is carried along between the two

rollers

2 and 3, thus applying to the inking roller 2 a compression d+h. The pressure p between these two rollers varies between the points A and B representing the limits of the compression zone of the inking roller 2, as shown in FIGURE 3.

A theoretical calculus, assuming that the ink feed roller 3 is stationary (1 :0) and that a throttled flow of ink takes place between these two rollers, leads to the following relationship:

wherein K is a constant and l1, the thickness of the ink film between the two rollers when speed v =0.

If the curve h =f(d) is traced, the diagram of FIG- URE 4 will be obtained. In this figure, the squeezing d of the inking roller, before introducing any ink, is plotted in abscissa against the thickness h of the ink film between the two roller, in ordinate.

It will be seen that curve h =f(d) has an oblique asymptote if d has negative values corresponding to the existence of a gap between the

rollers

2 and 3.

If d has positive values corresponding to the application of pressure between

rollers

2 and 3, this curve will admit to infinity the axis of the values of d as an asymptote.

It will be seen that beyond a given value of d, that is, when the pressure between

rollers

2 and 3 exceeds a certain threshold, a considerable variation Ad of d involves a very small variation Alto of h On the other hand, considering the thickness e of the ink film at the outer periphery of inking roller 2 beneath point B, the following relationship can be easily determined according to the law of the mechanics of fluids. From this relationship it is clear that the thickness 2 of the ink film may be varied by modifying the ration v /v An experimental equipment designed for controlling the theoretical results obtained by calculation will now be described, the results of the tests carried out with various types of ink being given thereafter.

This experimental equipment is shown in diagrammatic form in FIGURE 5, wherein the component elements corresponding to those of FIGURE 1 are designated by the same reference numerals. The inking and ink-

feed rollers

2 and 3 revolve in the same direction at speeds v and v respectively. The inking roller 2 is lined with rubber and adapted to supply ink to the plate; in practice, its speed is subordinate to the plate speed and therefore to the machine speed. The ink feed roller 3 is chromiumplated to withstand the frictional contact of doctor 12 and acts accessorily as a wiper; its speed v will be adjusted to vary the ratio v /v and therefore the thickness e of the ink film deposited on the outer periphery of inking roller 2. The purpose of the measurements made during these tests was to study the variations in the thickness of the ink film left on the inking roller 2 after the wiping thereof by roller 3. To this end, for a given ratio and ink grade, the two

rollers

2 and 3 are moved towards each other (by means of the hydraulic cylinder or actuator 10 of FIG- URE 1) in order to obtain firstly a negative pressure therebetween when these rollers are somewhat spaced from each other, then a certain positive pressure when the inking roller 2 is squeezed by the ink feed roller 3.

The position of ink feed roller 3 is checked by means of two comparators 17 disposed at either end of roller 3. The compression d of the inking roller 2 is positive when the distance between centers of these rollers is smaller than the theoretical or actual value R +R and negative in the other alternative.

The thickness of the ink film carriedby the surface of the inking roller 2 after the wiping action produced by the ink feed roller 3 is determined by means of a cup 18 held in contact with the surface of the inking roller 2 during a number of revolutions N of this roller, whereby its leading edge having alength a will scrape off completely any ink left on the surface of inking roller 2. Thus, all the ink carried by a surface corresponding to a 2R N is collected. Weighing this ink will give, by means of a very simplecalculation, the average thickness e of the ink film during N revolutions.

' The results of these measurements concerning two types of ink are given hereinafter.

F irst test This test was carried out under the following conditions:

Velocity of rotation of inking roller 2 v =2O m./mr1. Velocity of rotation of ink feed roller 3 v and v =m./mn. Hardness of rubber lining of roller 2 u Shore No. 45 Radius of inking roller 2 R =65 mm. Radious of ink feed roller 3 R =65 mm. Ink viscosity 2poises.

The results are summarized in Tabe I hereinafter and also in the diagram of FIGURE 6 of the attached drawing, wherein the squeezing d in mm. is plotted in abscissa against the thickness e of the ink film in ordinate. In this diagram, curve A corresponds to a ratio v /v =0 and curve B to a ratio v /v =.5.

c e (microns) (microns) Second test This test was carried out under the following conditions:

Velocity of rotation of inking roller v =30 m./mn. 2 v =variable Velocity of rotation of ink feed roller from 0 to 21 m./mn. Hardness of rubber lining of roller 2 Shore No. 45. Radius of inking roller 2 R =65 mm. Radius of ink feed roller 3 R =65 mm. Ink viscosity 2poises.

The results are summarized. in Table II hereinafter and also in the diagram of FIGURE 7 of the attached drawing, wherein the curves C, D, E, F and G correspond to the following values of ratio v /v 0; .15; .3; .5; .7.

TABLE II d velvt=0 v../vt=0. 15 71e/ t=0. 3 Ila/=0. 5 .ve/vt=0. 7 mm.

c e e s e (a) (F) (u) (a) (u) in ordinate.

The curve H is a straight line corresponding to the theoretical law ah 19) e- 2 1 m determined by calculation, and curve I obtained by inter connecting the points found experimentally is determnied from the curves of FIGURE 7.

Therefore, to obtain on the peripheral surface of inking roller 2 an ink film 6 having a strictly constant thickness throughout the length of this roller, the following procedure must be adhered to: After having poured a reserve or fountain of ink 5 above the nip of

rollers

2 and 3 in muaual contact, the cylinder or actuator 10 is actuated in order to produce in said nip 4, between the

rollers

2 and 3, a pressure higher than the critical pressure threshold beyond which any additional increment of said pressure does not produce any appreciable variation in the thickness of the ink film. To this pressure threshold corresponds a given value d of the'rubber squeezing which may be selected, for example, from the set of curves of FIGURE 6, to be 0.8 mm. The pressure exerted by the cylinder 10 should be sufficient to cause the local pressure exerted at any point along the contact generat rix 4 to exceed said critical pressure threshold, so that, irrespective of the deformation to which the

rollers

2 and 3 are subjected by this pressure, the thickness e of the ink film 6 remains constant throughout the length of the inking roller 2. This thickness, which is for example 4.89u (see Table I, and FIGURE 6) for a squeezing sag d =0.8 mm. and a speed ratio v /v,=0, may be adjusted to the desired value lower than 4.89;]. by adjusting the velocity of rotation of the wiper roller 3 after the curve I of FIGURE 8. The higher the velocity of rotation of ink feed roller 3, the thinner the ink film 6.

Thus, the experiment confirms the fact that the varia. tion in the thickness e of the ink film is immaterial in sprite of considerable differences in the squeezing value d, when d exceeds a predetermined critical value.

The mechanical defects such as eccentricity, fiexion, etc. likely to alter d (value of initial squeezing or pressure chosen initially) may be several tenths of .a millimeter without inasmuch interfering with the regularity of the ink layer.

In fact, it may be said that when a roller or cylinder is out of true by about .05 mm. this value is considerable.

On the other hand, a one-meter long steel roller having a diameter of 100 mm. and to which a load corresponding to one millimeter of squeezing is applied will yield only by .05 mm.

The variation in the flexible roller squeezing d as a consequence of mechanical defects would therefore total only .1 mm.

Now if we refer to the diagram of FIGURE 7, it Will be seen on curve B corresponding for example to a ratio v /v =.3 for a variation Ad=.l mm., the variation in the ink film is of the order of which is negligible.

FIGURE 1 shows that the doctor 12 substantially prevents any ink film from continuing to adhere to the outer surface of roller 3 after this doctor 12. However, if the ink film is not removed completely as shown in FIGURE 1 another doctor 13 may be provided which has its operat-ive end disposed tangent to the ink feed roller 3 in the zone where the generatrices of this ink feed roller 3 move downwards, that is, on the right-hand side of this roller as seen in FIGURE 1. This additional doctor 13 makes a completely ink-free surface :after it, and may also serve a complementary function when it is desired to remove the reserve of ink 5. In fact, in this case the doctor 12 is simply removed while allowing the ink feed roller 3 to rotate in the clockwise direction. Thus, the ink reserve 5 is carried along by the peripheral surface of this ink feed roller 3 towards the additional doctor 13 which collects this ink and directs same towards the discharge through 14.

Although the attached drawings show two

separate motors

11 and 19 for driving on the one

hand rollers

1 and 2, and on the other hand roller 3, it will readily occur to anybody conversant with the art that the ink feed roller 3 may also be driven from the same motor 11 rotatably driving the inking roller 2 by providing to this end a variable-speed gearing in the transmission system between the motor and the ink feed roller 3.

-In the foregoing reference is made primarily to the supply of ink to the inking roller of an offset machine. However, it would not constitute a departure from the basic principles of this invention to apply this invention to the distribution of a regular, thin film of high-viscosity fluid on a cylinder or roller line with or consisting of relatively flexible elastic material.

Furthermore, although the present invention has been described in conjunction with preferred embodiments, it is to be understood that 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 appended claim.

What I claim is;

A device for distributing a thin regular film of a highviscosity liquid on the surface of a roller of flexible material, which is applicable notably to the inking of a fattyink printing machine and comprises a distributor and wiper roller of relatively hard material tangent to said roller of flexible material along a contact line, an ink fountain overlying said contact line, means for rotatably supporting said roller of flexible material and said distributor and wiper roller at their ends, means for rotatably driving said roller of flexible material and conveying a liquid film directly from said contact line, without using any intermediate equalizer roller engaging said roller of flexible material, means for rotatably driving said distributor and wiper roller in the same direction as said roller of flexible.

material, a doctor disposed with its operative edge engaging the peripheral surface of said distributor and wiper roller above said contact line and in the vicinity of said ink fountain, said roller 0f flexible material and said distributor and wiper r-oller exerting on each other a pressure adapted to form on the surf-ace of said roller of flexible material, throughout its length, a liquid film of constant thickness independently of the variation in the local contact pressure between said distributor and wiper roller and said roller of flexible material along their contact line, and means for varying the velocity of rotation of said distributor and wiper roller in relation to that of said roller of flexible material in order to control the thickness of the liquid film coating said roller of flexible material.

References Cited by the Examiner UNITED STATES PATENTS 1,780,695 11/1930 Alger l01350 1,873,235 8/1932 Wood 10135O 2,513,394 7/1950 Barrett et al 1l8262 X 2,531,036 11/1950 Goettsch 118-262 X 2,674,299 4/ 1954 Bruker 118262 X 2,830,555 4/1958 Barrett 1l8262 X 2,842,092 7/1958 Pomper 118262 X 2,870,738 1/1959 Jacobs et al. 118262 X ROBERT E. PULFREY, Primary Examiner.

J. R. FISHER, Assistant Examiner.