US3002450A - Rotary offset multi-color printing machines - Google Patents

Description

Oct. 3, 1961 P. PAPA ET AL ROTARY OFFSET MULTI-COLOR PRINTING MACHINES Filed March 2, 1960 2 Sheets-Sheet 1 Oct. 3, 1961 P. PAPA ET AL 3,002,450

ROTARY OFFSET MULTI-COLOR PRINTING MACHINES Filed March 2, 1960 2 Sheets-Sheet 2 3,002,450 ROTARY OFFSET MULTI-COLOR PRliNTlNG CHINES This invention relates to a mechanical device for use in connection with rotary offset printing machines comprising a feed board provided with oscillating sheet engaging grippers, a plurality of impression cylinders and associated sheet transfer cylinders provided with grippers engaging the edge of the sheet to be transferred.

It is known that one of the most stringent requirements in rotary offset printing machines of this type is accuracy of register in transfer of the sheet from a printing component to the next one.

In other words, the successive colors should be constantly printed on the sheets in identical positions to avoid any though slight alteration of the contour defining the printed regions.

The difliculties met with in insuring accurate register are of various kinds and chiefly depend upon the manner of transferring the sheet from a printing component to the next one.

In rotary offset printing machines of the type mentioned above inaccuracy in register is the result of slight displacements of the sheet as it is being transferred from a set of grippers to the next ones. The most frequent cause for such displacements resides in incorrect radial spacing of the stops on the grippers of the transfer cylinders and stops on the impression cylinders which either deliver or receive the sheet, respectively.

In known machines this spacing is a fixed tone but can exceptionally be adjusted on each of said members separately. This is a difficult manipulation from which uneveness of adjustment may result. Consequently, the radial spacing of the stops on the grippers of two contiguous rotary members may be inadequate to the thickness of the sheet to be printed. This disoonformity results in corrugation of the. sheet, hence inaccuracy in register, possibly even crimping of the sheet when the latter is pressed by the cylinders for printing. Moreover, adjustment should in any case be carried out while the machine is stationary.

This invention provides a device for effecting simultaneously by one manipulation during operation of the machine adjustment of all spacings of the stops on the rotary grippers transferring and receiving the sheet, respectively, depending upon the sheet thickness, as well as adjustment of the spacing of the stop on the oscillating grippers and feed board.

The improved device is advantageous over prior devices in that the machine can be very quickly adjusted to suit the varying sheet thickness, and identical variations can be effected of the spacing of all stops on all rotary grippers and of the spacing of the oscillating grippers and feed board.

The improved device chiefly comprises a centralised control leverage adapted to effect micrometric radial displacements of the stops on the rotary grippers of the transfer cylinder next to the impression cylinder, on each printing unit, and relative displacements of the feed board and stops on the oscillating grippers as well of the latter and stops on the grippers of the impression cylinder of the first printing unit even during operation of the machine.

The components \of the leverage of the adjusting mechanism are conveniently provided with eccentric bushings adapted to reduce deformations of the components, which results in high accuracy of the device.

Further characteristic features and advantages will be Stacs ate Patented Oct. 3, 1961 ice 2 understood from the appended description of the device in connection with a rotary offset printing machine with reference to the accompanying drawings given by way of a non-limiting example, wherein:

FIGURE 1 is a diagrammatical elevational view of a rotary offset printing machine equipped with the improved device,

FIGURES 2 and 3 are detail views of the leverage,

FIGURE 4 is a perspective view showing a sheet tumbling cylinder and associated drive for controlling radial displacements of the stops on the grippers,

FIGURE 5 is a detail view of FIGURE 4,

FIGURE 6 diagrammatically shows the deformation which may be undergone by the sheet as it is transferred from a cylinder to another.

The construction shown comprises two printing units 1, 2 arranged to print two different colors.

Unit 1 is fed with sheets from a pile 3 in a metal frame 4.

The sheets are taken from the pile 3 in a known manner by means of separating and gripping members fed from a pneumatic device not shown on the drawing. The frame 4 is connected with the printing unit 1 by a feed board 5 provided with conveyor bands. The sheets reach over the feed board a first impression cylinder '6, the sheets being taken over from the board by oscillating grippers 7 which rotate about their fulcrum 8 in the direction of the arrow F. The sheets thereby acquire a speed matching the peripheral rate of speed of the cylinder 6, so that they can be gripped without being damaged by the grippers on the cylinder 6, said grippers not being shown on the drawing.

The cylinder 6 rotates in the direction of the arrow C and moves the sheet into contact with a rubber cylinder 9 printing the first color. The rubber cylinder contacts in turn a cylinder 10 carrying a printing plate which is inked by means of suitable rollers not shown on the drawing.

The printed sheet is transferred from the cylinder 6 to a first transfer cylinder 11 comprising a hollow cylindrical member having two circular end discs interconnected by longitudinal shafts extending in the direction of the generatrices of the cylinder, carrying a plurality of grippers which engage the sheet on the cylinder 6. V

The sheet is transferred from the transfer cylinder 11 by means of further transfer cylinders 12, 13 carried by the printing unit 2 to a second impression cylinder 14 cooperating in the manner described above with a rubber cylinder 15 and a further cylinder 16 carrying the printing plate.

Further printing units of the same type as units 1 and 2 can be added for multi-color printing.

The sheet reaches from the last impression cylinder 14 a chain 1-7 which is likewise provided with grippers and is adapted to convey the printed sheet onto a pile 18. 19, 20 and 21 denote tie-rods included in the improved adjustment mechanism.

The device operates in the manner explained above to vary the spacing of stops 7a 011 the oscillating grippers 7 and feed board 5, as well as the relative radial spacing of stops 33 on the grippers carried by transfer cylinders 11, 13 and stops on adjacent cylinders (612-14).

The variation is required to prevent corrugation of the sheet as shown on FIGURE 6 resulting from incorrect spacing of the stops on the grippers of two consecutive cylinders on variation of the sheet thickness. This drawback is avoided by adjusting the radial spacing h to suit it to the thickness of the sheet being printed.

The improved device includes a cam 22 freely arranged on the shaft of each transfer cylinder, capable of phase displacement on said shaft through a conveniently limited angle.

Phase displacement of the cam 22 is effected by means 3 of a tie-rod 20 pivoted at 23 to a lever 24 securedly fixed to a bushing 25.

The bushing 25 is rotated for proper adjustment by means of a worm screw 26 on a shaft 27 having keyed thereto a control hand-wheel not shown on the drawing. The worm screw 26 meshes with a worm wheel sector 28 formed in the bushing.

The bushing 25 rotates over'a lever 29 eccentrically pivoted at 34 to the bushing 25 and over tie-rod 19 an eccentric bushing 30 which acts to displace a shaft 31 having arranged thereon a bearing 32 to which oscillating grippers 7 and stops 7a are attached. Rotation of the eccentric bushing 30 moves the bearing 32 in a direction perpendicular to the feed board to position the stop on the grippers a predetermined distance apart from the feed board to suit the thickness of the sheet being printed.

Rotation of the cam 22 radially displaces stops 33 on the grippers of the transfer cylinder 11.

The stops 33 are keyed in a parallel and suitably spaced relationship on a shaft 34 supported by a lever 35 pivoted to a shaft 36 having further pivoted thereto grippers 37. The free end of the lever 35 is retained by a spring 38 and is provided with a roller 39 close to a further roller 40 eccentrically carried by a lever 41 articulated to a pivot 4-2 and provided at its free end with a further roller 43 biased into contact with the operating profile of the cam by a spring 44.

The drive including the levers 35 and 41 is fast with the end discs of the transfer cylinder and rotates therewith with respect to the stationary cam 22.

The cam 22 is formed with two identical operating profiles 22a, 22b adapted to effect radial displacement of the stops 33 the moment the latter are situated on the straight lines connecting the centre of the transfer cylinder 11 wih the centres of the cylinders 6, 12, respectively.

Rotation of the cam 22 is transmitted through tie-rod 21 to a further cam 45 arranged on the shaft of the transfer cylinder 13. By means of further tie-rods it is possible to shift angularly further cams associated with transfer cylinders on each of any further printing units which may be provided on the machine.

Rotation of the bushing 25 consequently effects simultaneous and micrometric variation in spacing of the stops 7A on the oscillating grippers and feed board 5, as well as of the stops 33 on the rotating grippers and stops on grippers, not shown on the drawing, carried by the cylinders transferring the sheet to the transfer cylinders 11, 13 or receiving the sheet from the latter, respectively.

The control hand-wheel (not shown) keyed to the shaft 27 is conveniently provided with a pointer movable over a scale on which the varying thickness of the sheets to be printed can be read.

The improved machine is pre-set for printing sheet of varying thickness by acting on the hand-wheel to move the pointer to the graduation on the scale relating to the thickness of the sheet to be printed. This operation can be carried out while the machine is in operation.

What We claim is:

1. In a rotary offset multicolor printing machine comprising a number of successive printing units having impression cylinders rotating in the same direction and equipped with sheets gripping units comprising movable grippers and cooperating stops, a feed board arranged at the inlet end of the machine near the impression cylinder of the first of said printing units, an oscillating sheet gripping unit comprising grippers and cooperating stops lying between said feed board and said impression cylinder for taking up the sheets from said board and transferring them to the said cylinder, transfer cylinders between the impression cylinders of successive printing units and sheet gripping units comprising grippers and cooperating stops for said transfer cylinders, the said oscillating sheet gripping unit being mounted displaceable with respect to said feed board and said sheet gripping units of the transfer cylinders rotating in a direction opposite to the direction of rotation of the impression cylinders being mounted rockingly about axes parallel to the axes of said cylinders, means being further provided for displacing said oscillating sheet gripping unit and for simultaneously rocking the sheet gripping units for said transfer cylinders adjacent said impression cylinders thereby obtaining that the spacing of the stops provided in these sheet gripping units from the upper face of the feed board and respectively from the stops of the sheet gripping units provided on the other cylinders in the sheet transfer zones is suited to the thickness of the sheets being printed.

2. In a rotary offset multicolor printing machine comprising a number of successive printing units having impression cylinders rotating in the same direction and equipped with sheet gripping units comprising movable grippers and cooperating stops, a feed board arranged at the inlet end of the machine near the impression cylinder of the first of said printing units, an oscillating sheet gripping unit comprising grippers and cooperating stops lying between said feed board and said impression cylinder for taking up sheets from said feed board and transferring them to the said cylinder, said oscillating sheet gripping unit being mounted adjustable in height with respect to said feed board, transfer cylinders between said impression cylinders, sheet gripping units comprising grippers and cooperating stops for said transfer cylinders, the sheet gripping units of the transfer cylinders rotating in a direction opposite to that of rotation of said impression cylinders being mounted rockingly about axes parallel to the axes of said cylinders, cams rotatable about axes of said transfer cylinders carrying said rocking sheet gripping units, means interposed between said cams and said units for rocking said units upon rotation of said cams with respect to the associated transfer cylinders, said cams having two equal operative zones at which the spacing of the cam periphery from the axis of rotation of said cams varies, said zones being arranged angularly shifted in the same manner with respect to planes which comprise the axes of the transfer cylinders associated with said cams and adjacent other cooperating cylinders, thereby obtaining that the distance of the stops from the respective transfer cylinder axes and therefore from the stops of the sheet gripping units on the cylinders coopcrating with said transfer cylinders is the same when said stops pass through said planes upon rotation of said transfer cylinders, means being further provided for displacing said oscillating sheet gripping unit and for simultaneously rotating said cams about the axes of their associated transfer cylinders, whereby the position of the stops of said oscillating sheet gripping unit and the position which the stops of the sheet gripping units of the transfer cylinders rotating in opposite direction with respect to the impression cylinders assume at the time of sheet exchange with the adjacent cylinders may be simultaneously suited according to the thickness of the sheets to be printed.

3. In a rotary offset multicolor printing machine comprising a number of successive printing units having impression cylinders rotating in the same direction and equipped with sheet gripping units comprising movable grippers and cooperating stops, a feed board arranged at the inlet end of the machine near the impression cylinder of the first of said printing units, an oscillating sheet gripping means comprising grippers and cooperating stops lying between said feed board and said impression cylinder for taking up the sheets from said board and transferring them to the said cylinder, a shaft situated above said feed board and parallel to the axis of the impression cylinder of said first printing unit, a bearing arranged on said shaft and having secured thereto the grippers and the stops of said oscillating sheet gripping unit, and a rotatable bushing eccentrically supporting said shaft, whereby upon rotation of said bushing a variation in the spacing between said stops and the upper face of the feed board is obtained, transfer cylinders between the impression cylinders of successive printing units, and sheet gripping units comprising grippers and cooperating stops for said transfer cylinders, the sheet gripping units of each of the transfer cylinders adjacent to and rotating in opposite direction with respect to said impression cylinders comprising a shaft parallel with the axis of the transfer cylinder and fast with said cylinder and arranged near the periphery of the latter, said shaft having pivoted thereto the grippers of said sheet gripping unit, a rod parallel to said shaft supported radially displaceable of said transfer cylinder and carrying the stops cooperating with the last mentioned grippers, an arm pivoted at the end of said shaft laterally projecting beyond said transfer cylinder and having secured thereto at a point intermediate its ends an end of said rod carrying the stops, spring means urging said arm towards the axis of said transfer cylinder, a cam supported rotatably about the axis of said transfer cylinder and arranged near said arm, means interposed between the free end of said arm and the periphery of said cam for varying the angular position of said arm and therefore the distance from the cylinder axis of said rod and said stops according to the angular position of said cam with respect to the associated transfer cylinder, said cam having two equal operative zones at which the spacing of the cam periphery from the cylinder axis varies, said zones being arranged shifted in the same manner with respect to the planes which comprise the axis of said transfer cylinder and respectively the axis of one of the cylinders cooperating with the latter, thereby obtaining that the distance of the stops from the cylinder axis and therefore from the stops of the sheet gripping units on the cylinders cooperating with said transfer cylinder is the same when the stops of said cylinder pass through said planes upon rotation of said transfer cylinders, means being provided for simultaneously angularly shifting said rotatable bushing of the sheet gripping unit arranged near the feed board and said cams with respect to the axes of the transfer cylinders associated with said cams, whereby the position of the stops of said oscillating sheet gripping unit and the position which the stops of the sheet gripping units of the transfer cylinders rotating in opposite direction with respect to the impression cylinders assume at the time of sheet exchange with the adjacent cylinders may be simultaneously suited according to the thickness of the sheets to be printed.

4. A rotary offset multicolor printing machine as set forth in claim 3, wherein said means for simultaneously angularly shifting said rotatable bushing and said cams comprise a support fast with the stationary structure of said first printing unit a bushing mounted for rotation in said support and provided at its outer periphery with a worm wheel sector, a shaft rotatably mounted above said bushing and having provided thereon a worm screw cooperating with said sector, a hand wheel keyed to said shaft, a pointer on said wheel and a stationary scale indicating the thickness of the sheets to be printed cooperating with said pointer, an arm on said bushing, a rod pivoted to the end of said arm and to a point of the cam as sociated with one of the transfer cylinders offset from the axis of said cylinder, and a rod pivoted by its ends to the cams of each of two following transfer cylinders rotating in a direction opposite to the direction of rotation of the impression cylinder, and finally an eccentric pivot on the lateral face of said bushing, a lever pivoted on said pivot, and a tie rod pivoted at its ends to the free end of said lever and to the bushing of said oscillating sheet gripping device a point offset from the axis of the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,502,668 Harrold July 29, 1924 2,144,752 Dudley Ian. 24, 1939 2,577,099 Albrecht Dec. 4, 1951 2,699,939 Huck Jan. 18, 1955

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