US2933039A - Sheet transferring mechanism - Google Patents

Description

April 19, 1 c. c. CLAYBOURN ETAL 2,933,039-

snss'r TRANSFERRING MECHANISM Filed Aug. 21, 1958 INVENTORS CARLTON C.CLAYBOURN 27 3 BY ROMAN KOBOS ATTORNEYS SHEET TRANSFERRING MECHANISM Carlton C. Clayhourn, Northhrook, and Roman L. Kohos, Chicago, 111., assignors to Miehie-Goss-l)enter, Zircon pointed, Chicago, IlL, a corporation of Delaware Application August 21, 1953, fierial No. 756,383

8 Claims. (Cl. Nib-183) cylinder of one printing unit to the impression cylinder of the next unit by means of one or more successively coacting transfer drums, each of which is provided with grippers for engaging the leading edge of the sheet. These drums usually are of the same diameter as the impression cylinders and are formed with substantially continuous peripheral surfaces for supporting and controlling the body of the sheet during its travel between units. This type of transfer mechanism has proved to be highly efficient and very effective for transferring sheets in precise register, but it has a-tendency to cause the sheets to be smudged or smeared unless adequate preventive make ready is employed.

This condition is due to the fact that as each sheet is removed from the impression cylinder, after having received an impression, it is immediately conveyed in a reverse curvilinear path with its printed face in contact with the surface of the first transfer drum. Movement of the sheet is so rapid that the ink on the sheet does not have time to set before it contacts the transfer drum surface and, therefore, a portion of the ink adheres to or offsets onto the drum surface. Consequently, as the next sheet and all subsequent sheets are transferred, they may become smudged or smeared by the ink deposited on the drum surface by preceding sheets.

In the past, various make ready methods and devices have been proposed for reducing or eliminating this offsetting condition. One such method, for example, involved the use of emery cloth or like abrasive material on the surface of the transfer drum whereby to reduce the area of contact with the wet printed side of the sheet.

Still other methods are directed to the use of devices such as saw-tooth or serrated bands, star wheels, sheets with pointed staples. or tacks, and numerous other devices on the transfer drums whereby the printed side of the sheets would be supported at spaced intervals by the respective projecting particles or points. Such systems are effective to prevent offsetting for a short period of time, but after continued operation the ink may build up on the projections and unless the press is stopped periodically to remove the accumulations of ink, smudgingand smearing may re-occur. Moreover, because it is impossible to preclude all relative movement between the body of the sheet and the surface of the transfer drum, the projections cause scratches throughout the impression 'which .are readily apparent in the finished print.

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It is evident, therefore, that while the foregoing systerns might possibly alleviate the offsetting condition to some extent, they could never eliminate it completely for the simple reason that the respective: systems still require that contact be made with the printed side of the sheet. Moreover, the known systems require extensive make ready time before each job is started as well as for periodic cleaning which adds considerably to production costs.

Another mechanism which was developed for the pur pose of eliminating smudging of sheets during their transfer between units is disclosed in U.S. Patent No. 2,245,- 343. In this case a chain transfer mechanism is provided to transfer the sheets between the respective printing units and, no doubt, such mechanism would eliminate smudging because there is no surface for the printed side of the sheet to come in contact with during the transfer operation. However, such chain transfer mechanisms are not conducive to high quality printing because of their proven inability to maintain accurate register and thus, while use of such mechanism might eliminate smudging, it would introduce a more serious problem of maintaining accurate register of the sheets.

it is a primary object of this invention, therefore, to provide mechanism for transferring sheets between units of a multi-unit printing press whereby smudging of the sheets and the preventive make ready heretofore required are completely eliminated.

Another object of the invention is to provide an improved transfer mechanism which can be driven and controlled in a proven conventional manner to insure accurate register of the sheets.

A still further object resides in the provision of aerodynamic means for controlling and maintaining the body of the sheet in its normal path of travel and whereby contact with its printed face during the transfer operation is completely eliminated.

A further object is to provide a transfer mechanism comprising rotary gripper elements having a supporting shaft of substantially reduced diameter and which is so constructed and arranged as to effectively counterbalance the mass of the gripper assembly.

With these and other objects in View, the invention may consist of certain novel features of construction and operation as will be more fully described and particularly pointed out in the specification, drawings and claims appended thereto.

in the drawings which illustrate an embodiment of the invention and wherein like reference characters are used to designate like parts Figure 1 is a side elcvational View illustrating the sheet transfer mechanism as applied to a two-color rotary letterpress;

Figure 2 is a view taken substantially along line II-- II of Figure l, with the parts broken away to illustrat the construction; and v Figure 3 is an end view of Figure 2 showing the gripper actuating mechanism.

This invention is particularly adapted for use in conjunction with multicolor rotary printing presses of the unit type which may comprise as many as four or more printing units for printing a corresponding number of color impressions upon sheets of paper fed therethrough. For convenience, however, it is disclosed in Figure 1 as embodied in a conventional two-color rotary letterpress which is composed of two substantially identical printing units indicated as A and'B. The first unit A is adapted to print the first color impression upon each sheet and is comprised of an impression cylinder 10, a coacting plate cylinder 11, which carries the form to be printed, and an inking mechanism 12 which supplies the form with a fresh supply of ink before each impression. The secprinted side faces outwardly.

third transfer members.

nd unit B is adapted to print a second color impression in superposed relation on the same face of the sheet and is comprised essentially of an impression cylinder 13, a coacting plate cylinder 14, and an inking mechanism 15.

The sheets to be printed may be fed to the first impression cylinder by any conventional means, but in the preferred form this is accomplished by means of a stop gripper mechanism indicated at 16, which functions to engage the individual sheets while they are at rest in a registered position and to transfer them from the register table 17 to the impression cylinder grippers 18. The sheet is then carried on the impression cylinder to receive the first impression from the plate cylinder 11 whereupon it is transferred to the grippers 19 on the second impression cylinder to receive the second impression from the plate cylinder 14. After receiving the second impression the sheet may be conveyed to another printing unit, ifit is to be printed in three or more colors, or it may be transferred to a delivery sheet conveyor and carried to a delivery pile.

In accordance with the present invention the transfer mechanism for transferring the sheets between the respective printing units comprises three rotary transfer members 20, 21 and 22, each of which is provided with gripper elements for conveying the sheets in a curvilinear path from the grippers 18 of the first impression cylinder to the grippers 19 of the second impression cylinder. During its travel around the first and third transfer members 2t and 22 the sheet is carried with its printed side facing inwardly toward the axis of rotation, whereas, on the intermediate or second transfer member 21, its Therefore, the second transfer member may be a full size transfer drum having is substantially continuous surface for supporting the body of the sheet as it is carried about the axis thereof.

The novelty of this invention resides in the construction and mode of operation as regards those transfer members upon which the sheets are conveyed with their freshly printed side facing the axis of said members and which, in the present embodiment, comprise the first and Moreover, because these two members are substantially identical in structure and mode :of operation, the description will be directed to the first transfer member and corresponding prime numbers will be used to indicate the corresponding elements of the third transfer member.

In Figures 1 and 2 it will be seen that the transfer member 20 is provided with a series of gripper fingers 24 arranged in spaced relation on a gripper shaft 25 which is journalled for rotation in a series of radially projecting brackets 26 secured in spaced relation on the surface of a supporting shaft 27. A corresponding series of coacting gripper pads 28 are arranged in spaced relation on a gripper pad bar 29 which extends the full length of the supporting shaft 27 and is supported by a series of brackets 3-1 secured to said shaft. It will be noted that the respective brackets for the fingers and pads are adapted to project radially beyond the surface of the supporting shaft so that the gripper fingers and coacting pads will travel in a circular path having a radius equal to the radius of the impression cylinders and which path passes tangent to the impression cylinder 18 and the intermediate transfer drum 21 at the respective points of transfer. Consequently, as each sheet is'engaged by the grippers 24, it will be carried in a circular path and at the same surface speed as the impression cylinder.

The supporting shaft 27 is preferably formed from a hollow, tubular member of substantially reduced diameter with respect to the impression cylinder whereby to preclude contact with the printed side of the sheet and said shaft is provided with journal members 32 and 33 which are suitably mounted for rotation in the respective side frame members 34 and 35. As will be noted, particularly in Figure 2, in order to counterbalance the mass of the gripper and pad assemblies, the shaft 27 4 may be mounted eccentrically with respect to its journals, which latter are secured to said shaft by means such as the bolts 36, which are inserted through openings in the journal flange and threaded into tapped holes provided in the end plate 37.

Although the drive mechanism has not been shown, since it forms no part of the present invention, it will be understood that each of the cylinders and transfer members is provided with a conventional drive gear which is adapted to mesh with the corresponding drive gears on the adjacent members whereby they are all driven in unison and in precise timed relation. The present transfer members are conveniently adapted to such conventional drive mechanism and are thus provided with drive gears such as 38 whereby they are driven in precise timed relationship with their coacting impression cylinders. Moreover, conventional register segments, as indicated at 39, may conveniently be used whereby to accurately control the transfer members at the transfer points and thus insure precise register of the sheets.

As shown in Figure 3, the transfer grippers 24 are arranged to be opened and closed whereby to take and release sheets at the respective transfer points by means of a lever 41 which is fixed to one end of the gripper shaft 25 and carries a cam roller 42 which is adapted to travel about the periphery of a fixed control cam 43 secured to the adjacent face of the frame member 34. A spring 44, mounted on the rod 46, is adapted to exert a constant force between the boss 47 on the shaft 27 and the opposite end of the lever 41, whereby to maintain the roller 42 in contact with the cam and which is effective to open the grippers each time the roller '42 engages a low portion of the cam such as at 43:: and 43b.

It will be evident that as each sheet is transferred from the impression cylinder 10 to the intermediate transfer drum 21, its leading edge is under positive control of the curved shell or sheet control member 48 is mounted adjacent to the gripper path and which, as will be more fully explained hereinafter, is adapted to have coaction with the transfer gripper elements whereby to maintain the body of the sheet substantially coincident with the gripper path. The shell member may be formed of'any moderately rigid material such'as sheet metal or the like so as to have a continuous surface and said member is curved on a radius slightly greater than that of the gripper path so as to be concentric therewith. The shell is supported on transverse shafts 49 and 50 and is positioned as close to the path of the grippers as possible. In practice we have found that the best results and most positive control of the sheet is obtained when the space between the inner surface of the shell and the path of the gripper fingers does not exceed one-fourth inch. Moreover, the shell should extend around the-axis of the transfer member 20 substantially from the point of transfer at which said member takes a sheet from the impression cylinder to the point at which it releases the sheet to the drum 21.

.To facilitate positioning the shell as close to these points as possible, the leading and trailing edges: thereof may be notched, as shown in Figure 2, to provide clearance for 3 Originally it was assumed that centrifugal and gravitational forces alone would be sufiicient to maintain the body of the sheet against the shell member as it was being transferred. It was soon discovered, however, that pers, the action of the sheet was greatly improved. However, it was soon determined that the shell had to be positioned as close to the path of the gripper fingers as possible in order to maintain uniform velocity throughout the length of the. sheet. If the shell is spaced too far from the gripper path the trailing portion of the sheet obviously travels in a greater radius than the leading edge and thus at a faster rate. As long as the leading edge is engaged by the grippers 24 this differential of velocity has no adverse effect. When the leading edge is transferred to the grippers on the drum 21, however, the trailing portion of the sheet tends to advance on the leading edge, thereby creating a transverse wave in the sheet, the size and extent of which is directly proportional to the space between the shell 43 and the gripper path. As the space is reduced and more uniform velocity of the sheet established, the bulge or wave is eliminated. For optimum results it was determined that the space between the shell and the gripper path should not exceed a quarter of an inch.

Although the results achieved through the utilization of centrifugal force and the maintenance of uniform velocity throughout the length of the sheets were vastly improved, the action was not consistent and the body of the sheet would not always maintain intimate contact with the shell at all points as it was being transferred. Optimum results were finally achieved when the mechanism was arranged whereby to create a uniform, substantially reduced atmospheric pressure condition between the sheet and the shell member during the transfer operation. This was accomplished by providing a fiat rectangular bar for supporting the gripper pads and which was made to extend the full length of the shaft 27. This bar is mounted so as to project radially with its outermost edge substantially adjacent the-active faces of the gripper pads. Thus, as the transfer member rotates, the gripper pad bar functions much the same as the vane of a pump to remove a substantial amount'of the air from adjacent the inner surface of the shell. This in turn creates a reduced atmospheric pressure condition between the body of the sheet and the shell so that normal atmospheric pressure exerted against the exposed side of the sheet will effectively maintain it in intimate contact with the shell.

With certain grades of relatively stiff, heavy paper, the condition sometimes obtains that the trailing edge of the sheets will fall away from the shell, particularly as it approaches the second impression cylinder 13. At this point, it is substantially inverted and it is believed that the combination of gravity and resilience in the stiff sheets is responsible. Under such circumstances we have found it advantageous to direct a current of air against the sheet to supplement the effect of the atmospheric pressure thereon. Such air is supplied by means of an air knife 57 which is arranged adjacent the transfer point between the second transfer member 22 and the impression cylinder 13 and in a position that the current of air is directed against the sheet and in a direction counter to the direction of travel of the transfer grippers. Under no circumstances, however, should the volume of air be such as to destroy the effectiveness of the reduced atmospheric pressure condition between the sheet and the shell.

While we have herein illustrated our invention as comprising three successively coacting transfer members to transferrins the sheets between the respective impression cylinders, it will be appreciated that the number of transfer members is not a controlling factor. For example, a single transfer member such as 20 may be utilized to transfer the sheets directly from the impression cylinder 10 to the next succeeding impression cylinder 13, it working space between the respective units is adequate, in which case the drum 21 and the second transfer member 22 could be eliminated. Moreover, a single, double size transfer member could be utilized in a similar manner. in such event, two sets of oppositely disposed gripper assemblies would be provided, each of which would have the same coaction with a corresponding shell member for transferring the sheets. Therefore, the invention is not to be limited to or by details of construction of the preferred embodiment thereof illustrated by the drawings, as various other forms of the device will, of course, be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. Mechanism for transferring sheets in register from a first sheet carrying cylinder to a second sheet carrying cylinder comprising a series of coacting gripper elements for engaging the leading edge of a sheet, means mounting said gripper elements for rotation about a fixed axis in a circular bath having a point of tangency with both said cylinders, a concave shell member having a radius of curvature substantially equivalent to the radius of said gripper path, said shell member being mounted adjacent to the gripper path and extending substantially between said points of tangency, and means mounted for rotation with said gripper elements and having coaction with said shell member to create a reduced atmospheric pressure condition between the sheet and said member during the transfer of the sheet whereby normal-atmospheric pressure on the face of the sheet will maintain the body thereof in intimate contact with the surface of said member.

2. Mechanism for transferring sheets in register from a first sheet carrying cylinder to a second sheet carrying cylinder comprising a series of coacting gripper elements for engaging the leading edge of the sheet, means mount- -,ing said gripper elements for rotation about a fixed axis in a circular path having a point of tangency with both said cylinders, a concave shell member having a radius of curvature slightly greater than the radius of said gripper path and extending substantially between the said points of tangency, means for mounting said shell closely adjacent to said gripper path, and a transverse, radially disposed member mounted for rotation with said gripper elements and having coaction with said shell member to create a reduced atmospheric pressure condition between the sheet and said member during the transfer of a sheet whereby normal atmospheric pressure on the face of the sheet will maintain the body thereof in intimate contact with the surface of said member.

3. Mechanism for transferring sheets in register from a first sheet carrying cylinder to a second sheet carrying cylinder comprising a series of coacting gripper elements for engaging the leading edge of the sheet, means mounting said gripper elements for rotation about a fixed axis and in a circular path having a point of tangency with both said cylinders, said means comprising journals and a reduced diameter supporting shaft mounted eccentric with respect to the axis of said journals whereby to counterbalance the mass of said gripper elements, a concave shell member having a radius of curvature slightly greater than the radius of said gripper path and extending substantially between the said points of tangency, means for mounting said shell member closely adjacent to said gripper path, and means mounted for rotation with said gripper elements and having coaction with said shell member to create a reduced atmospheric pressure '7 condition between the sheet and said shell member during the transfer of the sheet whereby normal atmospheric pressure on the ,face of the sheet will maintain the body thereof in intimate contact with the surface of said member.

4. Mechanism for transferring sheets in register from a first sheet carrying cylinder to a second sheet carrying cylinder comprising a series of coacting gripper elements for engaging the leading edge of the sheet, a reduced diameter shaft for supporting said elements, said shaft being mounted for rotation whereby said gripper elements move in a circular path having a point of tangency with both said'cylinders, a concave shell member having a radius of curvature slightly greater than the radius of said gripper path, said shell member being mounted concentric with and closely adjacent to the gripper path and extending substantially between the said points of tangency, means mounted for rotation with said gripper elements and having coaction with said shell member to create a reduced atmospheric pressure condition between the sheet and the shell member during the transfer of the sheet whereby normal atmospheric pressure on the face of the sheet will maintain the body thereofin contact with said member, and means for creating a flow of air within said shell, counter to the direction of rotation of said gripper elements for controlling the trailing portion of said sheet.

5. In a sheet fed rotary printing press having two or more printing units coupled together for multi-color printing, mechanism for transferring sheets from the impression cylinder of one unit to the impression cylinder of the next unit comprising a transfer drum having the same diameter as the impression cylinders, a first rotary gripper means for conveying the sheets in a circular path from the first impression cylinder tosaicl transfer drum, second rotary gripper means for conveying the sheets in a circular path from said drum to the second impression cylinder, both said rotary gripper means having a supporting shaft of substantially reduced diameter with respect to the circular path of said gripper means to preclude contact between the surface of said shaft and the inwardly facing, printed side of the sheets, and a shell member arranged concentric with and closely adjacent to the paths of the respective rotary gripper means for maintaining the body of the sheet substantially in the path of said grippers, said rotary gripper means having coaction with their respective shell members as they rotate in close proximity thereto to create a reduced atmospheric pressure condition between the sheets and said shell members during the transfer of each sheet whereby normal atmospheric pressure acting upon the exposed face of the sheet maintains the body thereof against said shell members and in spacecl'relation with respect to said supporting shafts.

6. In a sheet fed rotary printing press having two or more printing units coupled together for multi-color printing, mechanism for transferring sheets from the impression cylinder of one unit to the impression cylinder of the next unit comprising a transfer drum, a first rotary gripper means for conveying the sheets in a circular path from the first impression cylinder to said transfer drum, a second rotary'gripper means for conveying the sheets in a circular path from said drum to the next impression cylinder, supporting shafts for said rotary gripper means having reduced diameters with respect to said drum and impression cylinders, and means for controlling the body of the sheets while they are being transferred by said rotary gripper means comprising a shell member formed concentric with and mounted closely adjacent to the paths of said rotary gripper means, and a transverse member mounted for rotation with said gripper means and having coaction with said shell member to create a reduced atmospheric pressure condition between the sheets and of gripper elements mounted for rotation in a circular path having points of'tangency with the first impression cylinder and said drum for conveying the sheets from said cylinder to said drum, 9. second series of gripper elements mounted for rotation in a circular path having points of tangency with said drum and the said next impression cylinder for conveying the sheets from the drum to the latter impression cylinder, supporting shafts for said gripper elements having reduced diameters with respect to said drum and impression cylinders, and means for controlling the body of the sheets while they are being transferred by said gripper elements comprising solid shell members arranged concentric with and closely adjacent to the paths of the respective gripper elements, said shell members extending substantially between the respective points of tangency, transverse members mounted for rotation with said gripper elements and having coaction with the respective shell members to create a reduced atmospheric condition between the sheets and said shell members during the transfer of each sheet, and means for creating a fiow of air Within the confines of said shell members and in a direction counter to the direction of rotation of said grippers whereby to maintain the trailing edge of the sheets in contact with said shell members and in spaced relation to said supporting shafts.

8. Mechanism for transferring sheets in register from a first sheet carrying cylinder to a second sheet carrying cylinder comprising, a supporting member mounted for rotation about an axis intermediate said cylinders with its surface spaced from the peripheral surfaces of said cylinders, a gripper assembly, means mounting said gripper assembly in radially projected relation on said supporting member for rotation in a circular path having a point of tangency with both said cylinders, a concave shell member mounted closely adjacent said path and, extending substantially between said points of tangency, and means for rotating said supporting member and therewith said gripper assembly whereby to transfer a sheet from said first cylinder to said second cylinder, said radially projecting gripper assembly having coaction with said shell member as said assembly rotates in close proximity thereto to create a reduced atmospheric pressure condition between the sheet and the shell member during the transfer of each sheet whereby normal atmospheric pressure actingupon the exposed face of the sheet maintains the body thereof in intimate contact with said shell member.

References Cited in the file of this patent UNITED STATES PATENTS

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