US2821134A - Offset printing press - Google Patents

Description

Jan, 28, 1958 G. R. BRODIE 2,321,134

' OFFSET PRINTING PRESS Filed Nov. 24, 1954 INVENTOR. George R. Brodie BY PM, almmd'q lwfmflzmaw-wf z A TORNEYS United States Patent OFFSET PRINTING PRESS George R. Brodie, Lower Merion Township,Montgomery County, Pa., assignor to Fredk H; LeveyCompany, Inc., New York, N. Y'., a corporation "of New York Application November 24, 1954, Serial No; 470,962

6 Claims.- (Cl. 101-217) This invention relates to printing, and-more particularly, to improvements in web-fed offset printing presses.

As is well understood in the art of offset printing, the ink is not applied directly by the printing plate to the paperweb, but is applied by the plate to a blanket, usually of rubber, which, in turn, passes in rolling contact with the web of paper passing over the impression cylinder and applies the ink thereto.

The blanket is wrapped around the circumference of what is known as the blanket cylinder which is rotatably' mounted on. an axis parallel to theaxis. of boththe vplate cylinder and the impression cylinder. and is so positioned.

that the circular blanket is rotated in simultaneous contact with the peripheries of each ofthe other two cylinders.

The blanket is appliedto the blanket cylinder by pass;-

ing it tightly around the periphery of the cylinder and securing its edges along a line in the periphery of the cylinder parallel to its axis. Clampinggmeans are custo:

marily provided along this line in the periphery of the" blanket cylinder for that purpose.

Due to the discontinuity and irregularities'of the blanket at the seam, it is necessary that the seam fall within a margin between the printed pages so as to-avoid'imp'er fections in the printed matter. To accomplish this, the blanket seam must be so positioned with respect to the printing plate on the plate cylinder as to fall, on each revolution of the blanket, in. a: margin: between the print-'- ing surfaces of adjacent pages: on the plate cylinder;

In spite of precautions tominimize irregularities in the periphery of the blanket cylinder at the: blanket seam,

there is always a noticeable vibration or: periodic. bump ing of the press, and particularly the blanket cylinder, at

the instant. the blanket seam passesthe plate cylinder.

In fine printing, and'especiallyinv high grade-multicolor work where precise register is required, the bumpingor vibration of the blanket cylinder is particularlytobjectionable as the resultingquiveringof the blanket in contact with the web causes a perceptible blurring of .the. ink

being applied at the point of contact between the blanket and impression cylinder.

My present inventionprovides improvements in printing presses of the type described'whereby the. objectionable blurring or imperfections in the printed matter due to this bumping of the blanket seam can be entirelyavoided.

In accordance with my present invention; this is accomplished by so designing and constructing the press that the inevitable bumping, causedby the passing of the blanket seam against the plate cylinder; will occur at an instant'when no printing istaking place, L e., at. an'instant when a margin between'pages is passing 'be tween the' blanket cylinder and the impression cylinder.

The invention isapplicable to embodiment in any rotary printingpress' for'ofiset printing where there are'two or more-pages around the printing cylindezji. re -margins around the plate cylinder, and the" plate cylinder and blanket cylinder are of equal circumference. Itz'will be understood that reference herein and inthe accompanying claims to circumferencesof theplateicylinder and blanket cylinder is intended. to mean;.thecircumference; ofithese cylinders? when ready: for i operations: i.. e.-, with. the: plate and the blanket, respectively, in position;

2,821,134 Patented Jan. 28, 1958 lhave found thatthe condition just described can be brought'about regardless of the number of pages around the plate cylinder, providing there are at least two margins, by, appropriate positioning of the plate cylinder axis with respect to the axis of the blanket cylinder and the impressioncylinder, respectively, and particularly with'respect to the angle between the plane passing through the axes of the plate cylinder and the blanket cylinderand the plane passingthrough the axes of the blanketcylind'er and the impression cylinder.

This angle will vary with the number ofJp'agesaroun'd' the plate cylinder but can,.in each instance, be calculated by dividing 360 by the number of margins around the cylinder and multiplying. the quotient by any whole number not greater than one less than the number of pages.

The invention will be further described andiillustrated by reference to thefollowiug drawings which represent conventionally and diagrammatically thatportion of a web-fed offset printing press to which my present invention is applicable 'and'of which Figure 1 represents a press design adapted to the use of'three pages, about the plate cylinder showing in dotted lines the appropriate arrangement for presses having six pages about'the plate cylinder; and

Figure 2 represents the design of that" portion of the press adaptedto the use of fourpages about the plate cylinder, showingiin' dotted lines the appropriate arrangement in presses having two or eight pages around the plate cylinder.

It will be understood that the cylinders and rollers shown in' the drawingare' rotatably mounted on shafts which are supported by press side-frames and: driven in the manner customary in rotary web-fed printing presses and, therefore, need not here be described in detail.

In Figure 1 of the drawings, the impression cylinder is indicated at 1, the blanket cylinder at 2 and the" plate cylinder at 3. Ink is supplied to the plate cylinder-by form rollers 4 to which ink is, in turn, supplied by the distribut= ing rollers 5 from a customary source. If printing is from planographic plates, water is supplied to the plate surface in thecustomary manner by rollers 6; ln' letter presses, the rollers 6 may be omitted.

The blanket is held tightly about the circumference of the blanket roller 2 by means of cl'ampinggjaws indicated at 7. The printing plate is secured in the' customary manner about the circumference of the plate cylinder 3 and the margins between the-pages are positioned at the intersections of the circumference ofthe cylinder and the three solid radial lines 8.

As the plate cylinder 3 rotates in contact with the blanket cylinder 2, the ink images of the respective pages are transferred to the blanket alongcorresponding segments of the circular blanket, the corresponding margins betwen' the pages falling at the intersections of the'circumference of cylinder 2 and the three solid radial lines 9.

As. previously noted, the blanket clamp on' roller 2 must fall at one of the margins between pages onthe plate cylinder 3. Since the plate'cylinder and the blanket cylinder are of equal circumference and are rotated at equal rates, the blanket clamp when'once placed at amargin between the pages will continue tofallon the same margin;

Itiwill b'e'seen' from the drawing that the'p'osition of the margins-of blanket cylinder 2, with respect'to impression cylinder 1, at the instance the blanket clamp 7"passes cylinder 3 will depend upon thepositiotr-of the axis of cylinder 3 and that by so positioning that axis that it lies ina' plane passing through the: axis. of cylinder" 2: at an angle: of. from a plane passing through the'axis ofiian. impression cylinder 1 and the blanket cylinder-2, one of the margins 9 of the blanket cylinder will pass in contact with the web on impression cylinder 1 at their;-

3 stant the vibration occurs due to the passing of the blanket clamp 7 in contact with the plate cylinder 3. Under no other coincidence can this condition occur, where there are butrthree margins around the plate cylinder.

Where there are six pages around the plate cylinder, instead of three, making three additional margins about the cylinders 3 and 2, respectively, as indicated by the dotted radial lines 10, the axis of the plate cylinder may be positioned identically with that just described for three pages. However, when using six pages, there are two other possible positions of the plate cylinder axis. One of these positions is shown in dotted lines at 11 with its axis in a plane 180 from the plane passing through the axis of cylinders 1 and 2, the margins between the pages being indicated in dotted radial lines 12 and the blanket seam at the instant of contact with cylinder 11 being indicated in dotted lines at 7 A further possible position using six pages around is that indicated in dotted lines at 13 lying in a plane forming an angle of 60 with the plane through the axis of cylinders 1 and 2, the six margins being indicated by the dotted radial lines 14, and the blanket seam at the instant of contact with cylinder 13 be indicated in dotted lines at 7".

In the construction represented in the drawing,v the periphery of plate cylinder 13 would interfere with the periphery of the impression cylinder 1. However, this condition can be avoided by using an impression cylinder of a smaller diameter, as indicated at the drawing at 1'.

In the foregoing and elsewhere herein, the angles specilied are measured clockwise from the plane extending to the left through the axes of the blanket cylinder and the impression cylinder. Like angles measured in the opposite direction may, of course, be used in the case of angles other than 180 C.

' Figure 2, in which like elements are indicated by the reference numerals used in Figure 1, represents in solid lines an arrangement adapted to presses having four margins about the plate cylinder 3 indicated by the solid radial lines 15, the cylinder 3 being placed with its axis in the plane forming an angle of 90 with the plane passing through the axes of the blanket cylinder and impression cylinder. An alternative position for plate cylinder having four margins is indicated in dotted lines at 17, the margins being indicated by the dotted radial lines 18. In either instance, when the blanket clamp-7 or 7 passes in contact with the plate cylinder, one of the other margins of the blanket cylinder will be in contact with the impression cylinder.

The position of the plate cylinder at 17 is also applicable to plate cylinders having two margins. The position of cylinders 3 and 17 are also applicable where eight pages around are used, resulting in four additional margins, as shown by the dotted radial lines 19.

Alternative positions of plate cylinders having eight margins are shown in dotted lines at 20, where the axis lies on a plane forming an angle of 135 with the plane passing through the axis of cylinders 1 and 2, and at 21 where the axis lies within a plane 45 from the plane through the axis of cylinders 1 and 2. In cylinders 20 and 21, the margins are indicated by the dotted radial lines 22, corresponding margins on the blanket roll being indicated by the dotted radial lines 23. I

As in Figure 1, the circumference of cylinder 21 when its axis is placed in the 45 plane would interfere with the periphery of cylinder 1. But this condition can be avoided by reducing the diameter of cylinder 1, as indicated at 1'.

As will readily appear from the drawings, in each of the indicated positions of the axis of the plate cylinder, the bumping due to the blanket seam striking the plate cylinder will occur at an instant when a marginal area of the blanket is in contact with the web passing over the impression cylinder.

Though I have illustrated my invention with respect to printing presses employing 2, 3, 4, 6, or 8 margins around the plate cylinder, it will be understood that the invention is not so restricted but is applicable to presses employing any number of pages of equal circumferential dimensions about the plate cylinder. Subject only to exceptions where there may be mechanical interference between the peripheries of the plate cylinder and the impression cylinder, the plane passing through the axes of the plate cylinder and the blanket cylinder should form an angle with the plane passing through the axis of the impression cylinder and the blanket cylinder, depending on the number of pages around the plate cylinder as set forth in the following tabulation:

i In the foregoing, I have, for simplicity, considered the blanket seam and the page margins as lines running longitudinally along the periphery of the respective cylinders. It will, of course, be recognized that this is not strictly in accordance with the facts. The lines considered are those passing through the center of the margins and of the blanket seam. The irregularity of the surface of the blanket cylinder, caused by the blanket seam, and which is responsible for the bumping heretofore referred to, may be an inch or more in width. The margins betweenpages will usually be at least as wide as said irregularity and frequently are somewhat in excess of the width of the blanket irregularity.

\ Consequently, depending upon the width of the respective margins, relative to the width of the irregularity of the blanket surface due to the blanket seam, minor deviations from the precise angles defined above, and in the appended claims, will be permissible without loss of the benefits of the invention. Translation of such periphal dimensions into degrees will, of course, depend on the radii of the plate and blanket cylinders. Usually a deviation, in either direction, of about 2 from the precise angles mentioned will be permissible, so long as no printing on the web occurs while the blanket seam is passing the plate cylinder.

I claim:

1. In a web-fed, ofiset-printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantial continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a'blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing images of pages of equal length, equally spaced circumferentially of the plate cylinder so as to provide equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression cylinder and the plate cylinder, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate. cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the'plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane passing through the axis of the I blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the im:

pression cylinder an angle determined by dividing 360 by the number of page margins about the plate cylinder and multiplying the quotient thereof by an integer not greater than 1 less than the number of said page margins, and thereby causing the blanket seam to pass in contact with the plate cylinder at an instant when no page image on the blanket is in contact with the web passing about the impression cylinder.

2. In a web-fed offset printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantially continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing images of two pages of equal length, equally spaced circumferentially of the plate cylinder so as to provide two equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression and the plate cylinders, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane passing through the axis of the blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the impression cylinder an angle of 180.

3. In a Web-fed offset printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantially continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing images of three pages of equal length equally spaced circumferentially of the plate cylinder so as to provide three equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression and the plate cylinders, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane passing through the axis of the blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the impression cylinder an angle of 120.

4. In a web-fed offset printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantially continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing images of four pages of equal length equally spaced circumferentially of the plate cylinder so as to provide four equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression and the plate cylinders, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane passing through the axis of the blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the impression cylinder an angle equal to multiplied by a whole number not in excess of 3.

5. In a web-fed offset printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantially continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing images of six pages of equal length equally spaced circumferentially of the plate cylinder so as to provide six equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression and the plate cylinders, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane pasing though the axis of the blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the impression cylinder an angle equal to 60 multiplied by a whole number not in excess of 5.

6. In a web-fed ofiset printing press comprising an impression cylinder, a blanket cylinder, and a plate cylinder rotatably mounted on parallel axes, each having a substantially continuous, smooth peripheral surface, means for passing a continuous web between the impression and blanket cylinders, the blanket cylinder comprising means for securing a blanket about the periphery thereof forming a blanket seam running parallel to the axis of said cylinder, the plate cylinder comprising means for securing to the peripheral surface thereof a printing plate bearing the images of eight pages of equal length equally spaced circumferentially of the plate cylinder so as to provide eight equal intervening page margins, the blanket cylinder being adapted to operate in rolling contact simultaneously with the impression and the plate cylinders, the circumference of the blanket cylinder, with the blanket attached, being equal to the circumference of the plate cylinder, with the plate attached, so that the blanket seam will invariably fall within a page margin on the plate, the improvement which comprises so positioning the axis of the plate cylinder with respect to the axes of the blanket cylinder and the impression cylinder that it will lie in a plane passing through the axis of the blanket cylinder forming with the plane passing through the axis of the blanket cylinder and the axis of the impression cylinder an angle equal to 45 multiplied by a whole number not in excess of 7.

References Cited in the file of this patent UNITED STATES PATENTS 939,553 Scheuerer Nov. 9, 1909 FOREIGN PATENTS 111,078 Great Britain Jan. 9, 1918 252,698 Italy Apr. 4, 1927

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