GB2038717A - A printing machine drive mechanism - Google Patents

Abstract

A multicolour rotary sheet printing machine comprises a plurality of printing units drivingly coupled by a wheel train. Drive means (15) extends alongside the wheel train and a mechanical oscillation filter (19) is connected between the drive means (15) at at least two input locations and respective printing units. The oscillation filter (19) may be a torsion bar (20) or other resilient coupling arranger between the force input point or its epicyclic gear arrangement and the impression cylinder 5. <IMAGE>

Description

SPECIFICATION A printing machine The present invention relates to a printing machine.

Drives are known for multicolour rotary sheet printing machines which are arranged in series and connected with one another by means of a closed wheel train and which are coupled by means of epicyclic gears associated with each printing unit with a main drive shaft driven by a motor, the epicyclic gears having unequal transmission rations.

Through these epicyclic gears, such a load branching for the individual printing units is obtained that a tooth flank bearing in one direction always takes place in the closed wheel train which connects the printing units with one another so that a substantial prerequisite is given for printing true to register (IT-OS 678 281).

Such devices have the disadvantage that, in spite of the defined tooth flank bearing, oscillations, which occur through unavoidable toothing errors, or errors, which occur through the rotation of shafts and wheels, are transmitted to the cylinders. Thereby, if one considers the printing machine as a multi-mass system, torsional movements arise between the individual masses, i.e. the cylinders and drums.

Through these disturbing oscillations, transfer errors in the transfer of the sheets between the cylinders and drums as well as inking stripes occur.

These disturbing oscillations act particularly unfavourably when the excitation frequencies and the natural frequencies of the printing machine are equally great in certain rotational speed ranges, i.e.

resonance is to be detected. Drives for multicolour rotary sheet printing machines with a series mode of construction of the printing units are also known, which are driven through a closed wheel train which is connected through at least two force input points with a drive train which extends parallel to the wheel train, is driven by the motor and which in the case of n force input points has n-1 torque limiters in the drive train or the torque limitation takes place softly, i.e. through compression springs, at n-1 force input points through coupling of the wheel train with the drive train.

Such loading branching is obtained for the individual printing units through the n-1 torque limiters that a tooth flank bearing in one direction always takes place in the closed wheel train which connects the printing units with one another so that an essential prerequisite is given for printing true to register (DD-PS 112 389).

Drives of that kind have the same disadvantages as the drives according to IT-PS 678 281, since force transmission from drive train to wheel train always takes pic ce without a soft coupling by reason of the fact that only n-1 torque limiters are provided.

According to the present invention there is provided a multicolour rotary sheet printing machine comprising a plurality of printing units drivingly coupled by a wheel train, drive means extending alongside the wheel train, and a mechanical oscillation filter connected between the drive means at at least two take-off locations and a respective one of the printing units.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a schematic illustration of a drive of a multicolour rotary sheet printing machine, Figure 2 shows a schematic illustration of the drive of a printing unit provided with an oscillation filter, and Figure 3 shows a contructional variant.

Referring to Figure 1, sheets stacked in a feeder 1 pass by way of an intermediate table 2, a rocker feeder 3 and the feeder drum 4 to an impression cylinder 5 of the first printing unit. The ink is transferred through a not illustrated inking device by way of the plate cylinder 7 and the offset cylinder 6 to the sheet disposed on the impression cylinder 5.

The sheet is then transferred by way of a transfer drum 8 to the respectively following impression cylinder 5 and printed on by a further colour. The sheet is then conveyed by way of a deposit drum 10 into the deposit 9 and there deposited on a stack 11.

The transfer of the sheets from the rocker feeder 3 to the deposit drum 10 takes place through grippers which are disposed on the impression cylinders 5 and the drums 4,8 and 10.

The quality of the printing depends substantially on the accuracy of the transferring of the sheets so that it is necessary that the tooth flanks of the gear wheels 36 and 40 of the drums 4,8 and 10 and of the impression cylinder 5, which form the so-called closed wheel train, always bear against one another in like direction, i.e. no tooth flank change or lifting off may occur. This is attained through so-called synchronizing devices. These synchronizing devices comprise epicyclic gears 13, which are disposed in a drive train comprising a main shaft 15.

The main shaft 15 comprises several parts and is driven by way of the V-belt pulley 16 from a motor (not shown). A certain output component is transferred at a first force input point 17 through the first epicyclic gear 13 by way of a first step-down stage 18 to the first impression cylinder 5. In a similar manner, a load component is also transferred to the second and third impression cylinder 5 through the second and third force input points 17, while the load component is transferred to the last printing unit 5 through the fourth force input point 17 without interposition of an epicyclic gear 13. Thetransmission ratios of the epicyclic gears 13 are different so that an excess of power, which is not consumed in the printing unit itself, is supplied through the first force input point 17.This excess is passed on by way of the wheel train which connects the impression cylinders 5 and the drums 8 and 10 with one another, through the entire printing machine and thereby effects an always like tooth flank bearing of all these gear wheels.

All gear wheels, shafts and bearings have unavoidable geometric errors in spite of greatest care in production. These errors are oscillation exciters for the drums 8 and 10 and cylinders 5,6 and 7 which serve for serving the sheet guidance and the ink transmission. Non-synchronous movements of these drums and cylinders occurs through these torsional oscillations welling up in the resonance range so that transmission errors of the sheets and inking disturbances occur. To filter out these disturbing oscillations, oscillation filters 19 are connected between the step-down stage 18 and the impression cylinder 5 in each force input point 17.Since the cylinder wheels 36, arranged on the impression cylinders 5, of the wheel train are rigidly connected with the impression cylinderS, it can also be said that the oscillation filters 19 are arranged between each force input point 17 and the wheel train.

Figures 2 and 3 show an embodiment of an oscillation filter 19 in the form of a torsion bar 20.

Unlike the embodiment shown in Figure 1, the step-down stage 18 is constructed not a spur wheel/worm wheel stage, but as spur wheel/bevel wheel/spur wheel stage. The main shaft 15 carries a sun wheel 21, which engages with planetary wheels 22, which are arranged on planetary shafts 23.

Arranged on the planetary shafts 23 are planetary pinions 24 which engage with a central wheel 25.

The central wheel 25 is disposed on a central shaft 39 which is connected through a coupling 26 with an adjacent length of the main shaft 15. The planetary shafts 23 are rotatablyjournalled in a planetary wheel carrier 27 which also carries a pinion 28 engaging the spur wheel 29. This spur wheel 29 is connected through a bevel wheel stage 30 with a cylindrical pinion 31 which meshes in the drive wheel 32. The drive wheel 32 is shape-lockingly connected with the torsion spring 20 which is connected at one end 33 with a tube 34. The tube 34 is connected with an axial limb 35 of the cylinder 5.

The connection of drive wheel 32, torsion bar 20, tube 34 and axial limb 35 is so structured that the length of the torsion bar 20 is fully effective as an oscillation filter 19.

It is also possible to provide the connection between the torsion bar 20 and the impression cylinder 5 on the side of the impression cylinder 5 disposed opposite the axial limb 35 so that the torsion bar 20 can be constructed to be longer and act more softly.

Rigidly connected with the axial limb 35 is the cylinder wheel 36, which belongs to the wheel train and meshes with the drum wheel 40 of the transfer drum 8, which likewise belongs to the wheel train.

Entraining member 37 which co-operate with abutments 38 fastened to the tube 34, are arranged on the drive wheel 32 for overload protection, especially for the staring-up and braking of the machine The entraining members 37 and abutments 33 may be dispensed with.

The manner of operation is as follows: The maim shaft 15 is set into rotation by the motor (not shown; in that case, the epicyclic gear 13 comprising the sun wheel 21, the planetary wheels 22, the planetary pinions 24, the central wheel 25 and the planetary wheel carriers 27, tries to set the central shaft 39 into motion as a static gear. The central shaft 39 can however assume only a rotational speed which is determined by the transmission ratio of the impression cylinders 5 respectively following one another, i.e. the planetary wheel carrier 27 is set into rotation through the wheel train, the torques in that case being divided up in accordance with the transmission ratio in the epicyclic gear 13 over the epicyclic carrier 27 and the central shaft 39.

The torque of the epicyclic gear carrier 27 is transmitted through the spur wheel stage 28 and 29, the bevel stage 30 and the spur wheel stage 31 and 32 to the torsion bar 20. After the torsion bar 20 has resiliently deformed, the rotary motion and the torque is transmitted through the tube 34 to the axial limb 35 and thereby to the impression cylinder 5.

The torsion bars 20 are dimensioned differently starting from the differentiated power being fed in to the individual force input points 17. The power excess fed into the first printing unit is transmitted through the cylinder wheel 36 rigidly connected with the axial limb 35 to the next following printing unit and assures a secure tooth flank bearing. This advancing of the power excess propagates through the entire printing machine.

The torsion bars 20 are so dimensioned that they filter out oscillations greater than 1 Hertz so that disturbances from the drive train can not be transmitted to the cylinders and drums. Thereby, faultfree inking true to register is obtained. The interposition of the torsion bar 20 takes place after all force input points 17.

Claims (7)

1. A multicolour rotary sheet printing machine comprising a plurality of printing units drivingly coupled by a wheel train, drive means extending alongside the wheel train, and a mechanical oscillation filter connected between the drive means at at least two take-off locations and a respective one of the printing units.

2. A printing machine as claimed in claim 1, wherein each oscillation filter comprises a respective torsion member.

3. A printing machine as claimed in claim 2, wherein each torsion member has a respectively different torsional stiffness.

4. A printing machine as claimed in claim 1, wherein each oscillation filter damper comprises a resilient coupling.

5. A printing machine as claimed in any one of the preceding claims, wherein each oscillation filter is such as to substantially prevent the transmission of oscillations having a frequency in excess of 1 Hertz.

6. A multicolour rotary sheet printing machine substantially as hereinbefore described with reference to and as illustrated in Figure 1 of the accompanying drawings.

7. A printing machine as claimed in claim 6 and modified substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.