GB2175288A - Rotary printing press sheet feeding system - Google Patents

Abstract

Sheets 3 are fed individually from a stack 1 and transported to a printing unit of the rotary printing press, by a feed roller 19 driven by a cyclically variable gear arrangement comprising two cooperating rolling bodies 29, 30 which are non-cylindrical with respect to their axes of rotation, one of the rolling bodies 29 being coupled to the press drive, and the other rolling body 30 being connected to an output shaft F11 on which is mounted the cyclically driven feed roller. <IMAGE>

Description

SPECIFICATION Rotary printing press sheet feeding system This invention relates to a sheet feeding system for a rotary printing press which picks up a single sheet from a stack and transports it to a printing unit of the rotary printing press, a cyclic-irregularity gear arrangement being provided which drives a feed roller of the sheet feeding system alternatingly with a minimum and maximum speed.

In sheet-fed printing presses, a sheet is usually passed to a gripper system of an impression cylinder, or to a cylinder upstream of the latter, more particularly, a suction device removes a sheet from a stack, and transports it to a feed mechanism, which tranfers it finally to the cylinder just mentioned. As printers prefer to use a maximum sheet length with a minimum printing cylinder diameter, there is very little time available for the sheet feeding operation.

It would be conceivable to run the feed mechanism at a fairly high speed, to perform the operation of feeding the sheet in a very short time. Such an approach has certain disadvantages, however.

Thus the rapid movement entailed means that the suction device virtually tears the sheet from the stack. There is accordingly no assurance that the suction device will properly pick up and hold the sheets as they are being removed from the stack, this being particularly the case when handling cardboard or thin papers.

In addition, the air resistance encountered when the sheets are rapidly removed may result in the sheets, particularly if they are of this paper, becoming wavy, so that they are liable to creasing when subsequently transported at high speed.

Consequently, the printer's aim is always to obtain the greatest possible period of time in which to remove the sheet from the stack slowly and calmly, yet to avoid speed differences in the transfer to the feed mechanism, as well as in the transfer to the gripper system of a cylinder of the press, or at least to minimize these differences to the greatest possible extent.

DE-OS 17 61 306 has become known, in this connection, as showing the state of the art. The feeder drive in this case comprises a cyclic-irregularity gear arrangement which drives the sheet singling and feeding means at an irregular speed while the drive gear is rotating at a regular speed. In this connection a further cyclic-irregularity gear arrangement is provided, downstream, to solve the problem of compensating to the greatest possible extent the relevant torsional moments, namely those arising within the cyciic-irregularity gear arrangement itself, and also those occurring as a result of the loading of the output components with the masses which require to be accelerated and decelerated.An essential element is an eccentric gear which produces the irregular output via a swivel ge & and an output gear, an eccentric coupler and an oscillating link being provided to ensure that the teeth are constantly in mesh.

Setting out from this state of the art, it is an object of the present invention to simplify further the drive for the sheet feed mechanism in question, and thus to achieve a design which is less expensive, though more reliable in operation and subject to less wear.

According to the present invention, there is provided a sheet feeding system for a rotary printing press which picks up a single sheet from a stack and transports it to a printing unit of the rotary printing press, a cyclic-irregularity gear arrangement being provided which drives a feed roller of the sheet feeding system alternatingly with a minimum and maximum speed, wherein the cyclic-irregularity gear arrangement comprises two cooperating rolling bodies which are non-cylindrical with respect to their axis of rotation, one of the rolling bodies being coupled to the press drive, and the other rolling body being connected to an output shaft on which is mounted the alternatingly driven feed roller.

It is possible with this sheet feeding system to reduce substantially the time required for sheet feeding. The time thus gained can be used to remove the sheet from the stack with less haste and to transfer it to the gripper system of the press with less haste.

In respect of the transfer of the sheet by means of the feed rollers to the gripper device of the printing unit, the present invention makes possible a particularly beneficial effect. Thus preferably the sheet is transferred to the gripper device, which has a front stop, when the rotational speed of the feed roller has fallen almost to its minimum speed.

The speed difference which still exists between the sheet and gripper device can then ensure that the sheet, as a result of a slight bulging, is reliably transferred.

The time taken to feed a sheet through the sheet feed mechanism can easily be altered, simply by replacing the rolling bodies by others of a slightly different size.

Further particular advantages and preferred or optional features will become apparent to the reader from the subsidiary claims and from the following more specific description taken together with the drawings to which it refers.

In the accompanying diagrammatic drawings, Figure 1 is a fragmentary side view of a rotary printing press provided with a sheet feed mechanism driven in accordance with the present invention, Figure 2 is a similar fragmentary view on an enlarged scale showing the use of two elliptical gears in the drive of the sheet feed mechanism, Figure 3 shows a further arrangement using two oval gears, Figure 4 shows a still further arrangement using an eccentric gear and an oval gear cooperating with it, Figures 5, 7 and 9 are graphs showing the ratios of the rotational speeds at the input and output ends of the drive, over one revolution of the drive pinion, and Figures 6, 8 and 10 are graphs showing the corresponding angular velocities.

Figure 1 shows a small offset printing press in which single sheets 3 pass from a stack 1 through a singling device 2 into a gap between a blanket cylinder 4 and an impression cylinder 5, where the actual printing takes place. The sheet 3 which is thus printed is then picked up by a chain distributor 7 provided with rows of grippers 6, and passed to a distribution stack 8. The printed image is transferred, with the aid of a moistening unit 9 and an inking unit 10 having an inking roller 11, which inks a plate cylinder 12, from the plate cylinder 12 to the blanket cylinder 4; the blanket cylinder 4 produces the impression by means of a blanket 32 held by a clamping device 23. A blanket washing device 13 is provided to cooperate with the blanket cylinder 4. An etching device 15 is provided for the printing plate 14.In addition a front feed device 16 for the printing plate 14 is provided which can cooperate with th,e plate cylinder 12. The press is controlled from a control desk 17 provided with an appropriate array of pushbuttons.

As may be seen from Figure 2, sheets 3 pass from the singling device 2 to a pair of feed rollers 18, 19, one of which, 19, is driven by the machine drive (not shown) as approximately the same rotational speed as the cylinders 4, 5 and 12. Thereafter a sheet 3 passes, by way of a guide channel 20, to a gripper device 21 of the impression cylinder 5. The circumference of the feed roller 19 is made somewhat greater than the distance 24 between tha feed roller gap 25 and the sheet transfer point 26. The reason for this is that sheet 3 has to catch up somewhat with the gripper device 21 of the impression cylinder 5.

Figure 2 shows the drive for the feed roller 19 by means of effective pitch circle lines (shown here as broken lines). The drive is derived from a gear 22 associated with the impression cylinder 5, and is transferred to a drive pinion 27. This is mounted on a drive shaft 28 on which, at a certain axial spacing, there is also mounted an elliptical gear 29.

The latter is mounted at one of its focal points.

This is shown at F1, its other focal point being shown at F2.

This elliptical gear 29 cooperates with a second eliiptical gear 30, which is mounted on an output shaft 33, which also serves as the mounting of the feed roller 19 being driven. The gear 30 too is mounted at one of its focal points. This is shown at F11, its other focal point being shown at F22.

The cross-section ratio of the gear 22 and drive pinion 27 is so selected that the angular velocity (ova) of the drive pinion 27 is an integral multiple of the angular velocity of the gear 22. The dimensions of the drive pinion 27 and elliptical gears 29 and 30 and the operative diameter of the feed roller 19 are so related that, for instance, in the position shown, the peripheral speed of the feed roller 19 is approximately the same as that of the impression cylinder 5 and thusapproximately the same as the printing speed.

The position shown in Figure 2 is that in which the sheet 3 is just being transferred to the gripper deive 21. From the moment when the sheet 3 is introduced into the feed roller gap 25, the elliptical gears 29, 30 have performed one revolution. The sheet 3 was previously separated from the stack 1 by means of suction heads 34, and was brought in by the latter being made to perform a swivelling action, around its axis of rotation 35, by a swivelling device 31 (not shown in detail here), which operates in the same rhythm as the remainder of the press. The two feed rollers, 18 and 19 then forward the sheet to the sheet transfer point 26 for the impression cylinder 5.At this moment, the top feed roller 18 is raised from the driving feed roller 19, by means of a further swivelling device 37, also operating in the rhythm of the press, being lowered again on to the feed roller 19 when the next sheet 3 is brought in. Roller 19 makes several revolutions in this non-loaded condition during this interval; this is due to the transmission ratios which are adopted, the number of revolutions made corresponding with the integral multiple of the abovementioned ratio between the gear 22 and drive pinion 27.

Figure 3 shows a variant for the drive of the feed roller 19. In place of two elliptical gears, two oval gears of equal size, 38 and 39, are provided in this case; each of these is mounted at the intersection point of its axes of symmetry 42 and 43. It must be noted in this connection that the angular velocity of the output shaft 33, and thus the rotational speed of the feed roller 19, passes twice through the respective minimum, and twice through the respective maximum, during the period wherein the drive pinion 27 performs one revolution at a constant angular velocity. Allowance has naturaily to be made for this point in deciding upon the transmission ratios; in particular the feed roller 19 has to have an operative circumference approximately twice as great as the distance 24 between the feed roller gap 25 and the sheet transfer point 26.The other feed roller 18 therefore has to be raised from the feed roller 19 in this case after the latter has performed only a half revolution.

Figure 4 shows a further embodiment of the rolling bodies which are non-cylindrical with respect to their axis of rotation. Here an eccentrically mounted gear 40, mounted on the drive shaft 28, cooperates with an oval mating gear 41 mounted on the output shaft 33. The gear 41 is mounted on the shaft 33 at the intersection point of its axes of symmetry 42 and 43. As there is a ratio of rotationai speeds of 2:1 between drive shaft 28 and output shaft 33, the angular velocity of the output shaft 33 and the circumferential speed of the feed roller 19 pass through two maxima and two minima in one revolution (= two revolutions of drive shaft 28). Particular allowance should be made for this fact when deciding upon the diameter of the feed roller 19 with respect to the distance 24 mentioned earlier.

Figures 5 to 10 represent, for the embodiments shown in Figures 1 to 4, the respective relationships between the angular velocities at the input and output ends (coy, o)b), i.e. the angular velocities of the drive and output shafts 28 and 33. Figures 5 to 10 also show the relationships between the printing speed (rotation speed of drive pinion), Va, and the rotational speed of the feed rollers, Vb, over one revolution (t = 360 ) of the drive pinion 27. Figures 5 and 6 relate to the embodiment of Figure 2; Figures 7 and 8 relate to the embodiment of Figure 3; and Figures 9 and 10 relate to the embodiment of Figure 4.The appropriate moment for transferring the sheet 3 by means of the gripper device 21 of the impression cylinder 5 is just before the lower vertex (minimum) of the rotational speed curve for the feed rollers 18 and 19, and this is indicated in Figures 5, 7 and 9 by the small circle marked 26 (this reference numeral refers to the sheet transfer point 26).

Another sheet transfer point, namely that for the transfer of the sheet 3 from the singling device 2 to the feed rollers 18 and 19, is indicated in Figures 5, 7 and 9 by the small circle marked 44. The rotational speed of the feed rollers here is the same as the printing speed.

It is a particularly simple matter to alter the heights of the vertices of the curves shown, i.e. to shorten the time of passage through the sheet feed mechanism, by using elliptical gears, oval gears and eccentric gears of different sizes.

It will be understood that the invention has been described above purely by way of example, and that various modifications of detail can be made within the ambit of the invention.

List of parts 1Stack 2Singling device 3Sheet 4Blanket cylinder Slmpression cylinder 6Row of grippers 7Chain distributor 8Distributing stack 9Moistening unit 101nuking unit lllnking roller 12Plate cylinder 13Blanket washing device 14Printing plate 15Etching device 16Front feed device 17Control desk 18Feed roller 19Feed roller 20Guide channel 2lGFipper device 22Gear 23Clamping device 24Distance 25Gap of feed rollers 26Sheet transfer point 27Drive pinion 28Drive shaft 29Elliptical gear 30Elliptical gear 31 Swivelling device 32Blanket 330utput shaft 34Suction heads 35Axis of rotation 36Gripper transfer point 37Swivelling device 380val gear 390val gear 40Gear 410val mating gear 42Axis of symmetry 43Axis of symmetry 44Sheet transfer point )a = Angular velocity of drive pinion or drive shaft

Angular velocity of output shaft Focal points of elliptical gears Rotational speed of feed rollers via = Rotational speed of drive pinion = printing speed t = Revolution of drive pinion (360 = 1 revolution)

Claims (8)

1. A sheet feeding system for a rotary printing press which picks up a single sheet from a stack and transports it to a printing unit of the rotary printing press, a cyclic-irregularity gear arrangement being provided which drives a feed roller of the sheet feeding system alternatingly with a minimum and maximum speed, wherein the cyclic-irregularity gear arrangement comprises two cooperating rolling bodies which are non-cylindrical with respect to their axis of rotation, one of the rolling bodies being coupied to the press drive, and the other rolling body being connected to an output shaft on which is mounted the alternatingly driven feed roller.

2. A system according to claim 1, wherein (in use) the sheet reaches a sheet transfer point for transferring the sheet to a gripper device of the printing unit at a stage immediately preceding a minimum in the circumferential speed curve of the alternatingly driven feed roller.

3. A system according to claim 1 or 2, which employs two cooperating feed rollers, these being the alternatingly driven feed roller and a non-driven feed roller, the sheet running into the gap between the feed rollers, and the non-driven feed roller being (in use) raised from the driven feed roller, and thereafter returned to it, in the same rhythm as the sheet feed.

4. A system according to claim 1, 2 or 3, wherein the drive for the driven feed roller is derived from a gear associated with the impression cylinder of the printing unit of the rotary printing press, and is transferred to a drive pinion, the latter being mounted on a drive shaft on which is also mounted the said one rolling body of the cyclic-irregularity gear arrangement.

5. A system according to claim 1, 2, 3 or 4, wherein the cyclic-irregularity gear arrangement comprises two cooperating elliptical gears whose axes of rotation pass in each case through one of the two focal points of the elliptical gear.

6. A system according to claim 1, 2, 3 or 4, wherein the cyclic-irregularity gear arrangement comprises two cooperating oval gears whose axes of rotation pass in each case through the point of intersection of the axes of symmetry of the oval gear.

7. A system according to claim 1, 2, 3 or 4, wherein the cyclic/ irregularity gear arrangement comprises an eccentrically mounted driving gear and an oval gear cooperating with the former, the axis of rotation of the oval gear passing through the point of intersection of its axes of symmetry, and a reduction ratio of two to one being provided in respect of the drive from the eccentrically mounted driving gear to the oval gear.

8. A system according to claim 1, substantially as described with reference to any Figure or Figures of the accompanying drawings.