GB2194516A - A printing machine sheet feed - Google Patents

Abstract

A printing machine (2) comprising a gate (60) for sequentially passing sheets of paper through the printing machine (2), and a head lay device (64) for engaging a front edge portion (66) of the sheets of paper (50) to cause them to lay correctly before they are printed by the printing machine (2). The head lay device (64) is able to advance or retard the sheets of paper in relation to the rotary movement of grippers (78) on impression cylinder (56). <IMAGE>

Description

SPECIFICATION A printing machine This invention relates to a printing machine.

There are various type of printing machine available from relatively simple duplicator type printing machines to very complicated multicolour printing presses. All of these known printing machine suffer from the disadvantage that difficulty may be encountered in sequentially laying sheets of paper on the printing machine so that they are correctly aligned and registered for printing purposes.

It is an aim of the present invention to obviate or reduce the above mentioned problem.

Accordingly, this invention provides a printing machine having a gate for sequentially passing sheets of paper through the printing machine, and a head lay device for engaging a front edge portion of the sheets of paper to cause them to lay correctly before they are printed by the printing machine.

The gate may have a shoulder portion against which the sheets of paper abut.

The head lay device may be able to advance or retard the sheets of paper in relation to an impression roller which forms a part of the printing machine.

A stepper motor arrangement may be employed to advance or retard the sheets of paper in relation to the impression roller.

The printing machine may be one in which the head lay device comprises a pivotable bar and a plurality of fingers which extend from the bar, the printing machine being such that the fingers move in and out of a series of complementary recesses in an impression cylinder of the printing machine as the bar pivots backwards and forwards.

The printing machine may include a pair of side adjustor devices for engaging the sides of the sheet of paper for assisting in laying the sheets of paper correctly before they are printed by the printing machine.

The side adjustor devices may be a pair of reciprocating devices which repeatedly knock against the sides of the sheet of the paper.

The side adjustor devices may operate via a cam and a lever arrangement.

The printing machine may have electronic control means for controlling the time at which the head lay device releases the individual sheets of paper to allow them to be gripped by gripper means which forms part of the printing machine and which pulls the individual sheets of paper through the gate and the head lay device for printing.

The electronic control means may comprise a visual aid for assisting an operator to set up the printing machine such that the head lay device correctly releases in relation to the time the gripper means operates to grip the individual sheets of paper, the visual aid com prising a pair of lights which are arranged to operate together when the head lay device and the gripper means are correctly syncronised, one of the lights being provided on a paper position sensor device and the other light being provided on a control panel of the printing machine. The paper position sensor device can be factory made and coars ely set to light up at the required time. Fine adjustment can then be made by the operator to get both lights to light up together.

The printing machine of the present invention may generally be any known type of printing machine that may, for example, print black and white reproductions or colour reproductions. Where multicolour, for example four colour, reproductions are being printed, a separate head for each colour will normally be employed. Thus, a four colour printing machine usually have four of the printing heads.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows somewhat schematically a printing machine having a single printing head; Figure 2 shows a gate and a head lay device; and Figure 3 shows a logic circuit which embodies logic circuitry for operating the gate and the head lay device shown in Figure 2.

Referring to Figure 1, there is shown a printing machine 2 comprising a plate roller 4, a reservoir 6 for water 8, and a fount roller 10 for transferring water 8 from the reservoir 6 to the plate roller 4.

The reservoir 6 and the fount roller 10 form part of a water unit 12 which also comprises a ductor roller 14, a nitrile roller 16, an oscillating roller 18 and a Molleton roller 20. The direction of rotation of the various rollers in the water unit 12 is shown by arrows in the water unit 12.

The plate cylinder 4 receives ink from an ink unit 22. The ink unit 22 comprises an ink fount roller 24, a ductor roller 26, a rubber roller 28, idler rollers 30,32, ink forme rollers 34, 36, a main oscillating roller 38, a rubber roller 40, and a distribution roller 42. The direction of rotation of the various rollers in the ink unit 22 is shown by arrows. The passage of ink from the ink fount roller 24 to the ink forme rollers 34, 36 is shown by two long arrows 44,46. In the ink unit 22, the roller 46 acts as an auxiliary oscillating roller.

Water which is placed on plate roller 4 via the water fount roller 10 and ink which is placed on the plate roller 4 via the ink fount roller 24 are transferred to the blanket roller 48. Paper 50 passes in the direction of the arrow 52 through the nip 54 between the blanket roller 48 and an impression roller 56.

The impression roller 56 operates in conjunction with a transfer roller 58. An image on the plate roller 4 is thus transferred to the paper 50. As is well known, the rollers 4,48 and 56 are sometimes referred to in the art as cylinders.

The paper 50 will usually come from a pile (not shown) of the paper and, once the paper 50 is printed, it will be delivered to another pile (not shown).

It will be seen from Figure 1 that the water unit 12 and the ink unit 22 are separate from each other so that the water and the inkare separately applied to the plate roller 4. The ductor rollers 14,26 move as indicated to be in driving engagement or non-driving engagement with the respective rollers 10,26 as will be understood. Obviously, as the plate roller 4 with its printing plate attached rotates, ink from the ink unit 22will be picked up by the cloth covered Molleton roller 20. Thus, at the roller 20, some milling of the ink and water will occur and this may be effective to give better printing under some printing conditions.

The fount roller 10 is advantageously constructed such that its direction of rotation can be reversed and this will obviously reverse the direction of rotation of the other rollers in the water unit 12, including the direction of rotation of the roller 20. This is effective to increase the milling action of the water and the ink and this increased milling may be effective to give yet further better quality printing. The printing machine 2 shown-in Figure 1 is a printing machine having only one printing head. The printing heads may be duplicated for each colour to be printed so that the printing machine 2 may have as many printing heads as there are colours to be printed.

Referring now to Figure 2, there is shown a gate 60 for sequentially passing sheets of paper 50 through the printing machine. The gate 60 has a shoulder 62 against which the sheets of paper 50 abut when the gate 60 is in its down closed position.

Figure 2 also shows a head lay device 64 for engaging the front edge portion 66 of the sheets of paper 50 to cause them to lay correctly before they are- printed by the rollers 4,48,56;58 as shown in Figure 1.

The head lay device' 64 is able to advance or retard the sheets of paper 50 in relation to the impression roller 56 as will-be described in more detail hereinbelow.

The -head lay device 64 comprises a pivota ble bar 68 and a plurality of fingers 70 which extend as shown from- the bar 68. The fingers 70 move in and out of a series of complementary recesses 72 in the impression roller 56 as the bar 68 pivots backwards and forwards.

As shown in Figure 2, the printing machine 2 includes a pair of side adjustor devices 74 for engaging the sides 76 of the sheets of paper 50 for assisting in laying the sheets of paper 50 correctly be fore they are printed by the printing machine 2. The side adjustor devices 74 are reciprocatory devices which repeatedly knock against the sides 76 of the sheets of paper 50. The side adjustment devices 74 operate via a cam and lever arrangement (not shown).

As will be described in more detail hereinbelow, the printing machine 2 includes electronic control means for controlling the time at which the head lay device 64 releases the individual sheets of paper 50 to allow them to be gripped by gripper means 78. The gripper means 78 is effective to pull the individual sheets of paper 50 through the gate 60 and the head lay device 64 for printing. The gripper means 78 comprise a series of gripper fingers 80 which extend from slots 82 in the impression roller 56.

An optical shaft encoder (not shown) is fitted to an end of the impression roller shaft 84. This optical shaft encoder indicates the positional status of the impression roller 56 to the logic circuits shown in Figure 3. The optical shaft encoder has three output signals, namely channel A, channel 8 and index. As the shaft 84 rotates, channel A gives out a string of pulses at the rate of 1000 pulses per revolution. Thus, for every revolution of the impression roller 56, channel A changes from logic high to logic low 1000 times. Thus 1000 pulses represent 360 rotation and tells the logic circuit that the impression roller 56 has rotated by 0.36 since the previous pulse.

Channel B also gives out 1000 pulses per revolution of the impression roller 56 but these pulses are 90 out of phase with those from channel A. By decoding the quadrature between these two strings of pulses, forward or reverse rotation of the impression roller 56 can be detected. The index output gives a single logic low pulse once per revolution at a preset position on the shaft 84. The position of this pulse is set to give a reference point on the impression roller 56. This is the point at which the fingers 70 of the head lay device 64 drop into the slots 72 in the impression roller 56. When the logic circuit receives the index pulse, it begins to calculate how far past the index the impression roller has travelled at any point in time. The logic circuit does this by counting the pulses from channel A. The logic circuit then uses this positional information, together with preset information, to determine the exact point at which the gate 60 and then the head lay device 64 are to be activated.

The printing machine 2 includes rotary switches (not shown in Figure 2) that are used to set the exact angle of rotation of the impression roller 56, after the index pulse, at which the gate 60 and then the head lay device 64 lift. Two -switches are used to set binary coded decimal information into the logic counter registers. The switches are provided to enable an operator to finally tune and set the lift point for both the gate 60 and the head lay device 64.

Each individual rotary switch may display a decimal number for each of its ten positions from 0-9. Each pair of switches are mounted side by side and display-a two digit decimal number from 00-99. The number displayed on each pair of switches indicates the number of pulses which must be counted from the encoder after the index point for the gate 60 or the head lay device 64 to lift.

As the encoder gives out 1000 pulses per revolution, in order to increase the pulse count and fine resolution, the logic circuit doubles this number of pulses giving 2000 pulses per revolution. Every pulse now represents 0.18 angle of rotation of the impression roller 56. It then follows that if the switches for the gate 60 are set to read 00, the gate will lift at 0 past the index. In other words, as soon as the index pulse is seen, the gate 60 will lift. If the switches are then set at 99, the logic circuit will count 99 pulses after the index pulse before the gate 60 will lift. This represents 99 x 0.18 of rotation of the impression roller 56 after the index point, or 17.82 maximum.Therefore the gate 60 can be set to lift at from 0 to 17.82 angular rotation of the impression roller 56 after the index point at 0.18 increments. Similarly, the angle of rotation of the impression roller 56 after the index point can be set by a second pair of switches, to lift the head lay device 64. As the head lay device 64 must be lifted after the gate 60 has been lifted, a preset fixed pulse count of 200, or 36 , is programmed into the head lay device lift registers. This 200 count is then added to the count set on head lay device lift switches. Therefore, if the se switches are set at 00, the head lay device 64 will lift at 200 plus 00 pulse count after index, equals 200 pulses or 36 after index.If the switches are set at 99, the head lay device 64 will lift at 200 plus 99, equals 299 pulses after index or 36 equals 99 x 0.18 equals 36 plus 17.82 equals 53.82". The head lay device lift point can then be set between 36 to 53.82 after index, in 0.18 increments.

It will thus be appreciated that the angle of rotation of-the impression roller 56 after indexing can be set under operator control to lift the gate 60 and then the head lay device 64 at the following points. Gate: 0 - 17.82 at 0.18 increments. Head lay: 36 53.82 .

Under normal printing conditions, the logic circuits will control the transfer of the sheets of paper through each printing head and the lay down of print on each sheet of paper 50.

For initial set up of the printing machine 2, prior to commencing a continuous print run, it is necessary to over ride certain areas of the logic control in order to establish ideal pre-run printing conditions. For example, the correct ink and damp lay ups and levels must be achieved manually before commencing a continuous print run. This facility is provided by the operator having manual over ride switches at the or each printing head. When one of these switches is activated, the relevant areas of logic and automatic control are bypassed.

The operator can then set up each perameter individually before starting automatic run under the logic control. There is thus provided an over ride switch for overriding the gate 60 and the head lay device 64 so that an operator can lift the gate 60 and the head lay device 64 together to allow unobstructed movement of the paper through the printing head, for example in order to enable the operator to clean the printing machine 2 or to clear a paper jam.

The angle at which the head lay device 64 sits when it has dropped into the slots 72 in the impression roller 56, controls the bite of the fingers 80 of the gripper means 78 on the paper 50. This angle can be adjusted at the or each printing head by driving a stepper motor 86, which is linked to the head lay device 64, either forwards or backwards. Two momentary push button switches may be provided, one of which drives the stepper motor forwards, advancing the angle, and the other of which drives the stepper motor backwards to retard the angle. By depressing the forward switch, a string of pulses are sent to the stepper motor 86 at the rate of one per second. Each pulse rotates the shaft of the stepper motor 86 by 7.5" forward.By pressing the reverse switch, a similar string of pulses is produced in order to reverse the stepper motor 86 by 7.5 per pulse. By using these two switches, the angle of the head lay device 64 and the bite afforded by the fingers 80 can be electronically set, even with the printing machine 2 running. Each step of 7.5 of the stepper motor 86 represents a change in angular position of 0. 118" and this allows registration fore and aft movement of 0.0015 inches.

Visual aid means (not shown) are employed for assisting an operator to set up the printing machine 2 such that the head lay device 64 correctly releases in relation to the time the gripper means 78 operates to grip each sheet of paper 50. The visual aid may comprise a pair of lights which are arranged to operate together when the head lay device 64 and the gripper means 78 are correctly synchronised.

One of the lights may be provided on a paper position sensor device which is factory assembled, and the other light may be provided on a control panel of the printing machine 2.

The lights are preferably light emitting diodes.

When the printing machine power is switched on, a power on reset circuit in the logic board immediately sets the head lay device output signal high. This is fed to the logic output board which switches head lay device 64 solenoids on, thereby lifting the head lay device 64. When the impression roller 56 revolves, the electronics are inactive until the electronics receive an index pulse from the encoder. As soon as this pulse is received, the head lay device output signal goes low, de-energising the solenoids and allowing the fingers 70 of the head lay device 64 to drop into their slots 72 in the impr ession roller 56.

The index pulse also loads the preset gate pulse count number from the above mentioned switches into the gate pulse counter register.

The gate pulse counter register then counts down from that loaded number, decrementing by two for every pulse received from the en coder channel A. When the gate pulse counter register reaches zero, the head lay output sig nal switches high, lifting the head lay device 64. Once the head lay device 64 has been lifted at this preset point, it remains up for the remaining angle of rotation of the impression roller 56, until the next index pulse is re ceived. Then the sequence is repeated.

Under normal running conditions, the head lay device 64 goes up and down once every revolution of the impression roller 56. If the gate 60 and-the head lay device 64 over ride switch is activated however, the logic control sequence is overidden and the head lay device 64 is maintained in an up mode. Similarly, if the printing machine reverse button is pressed, a signal from an overide relay imme diately lifts the head lay device 64 and the head lay device 64 stays up as long as the machine is being run in reverse. Also, a shut down condition lifts the head lay device 64.

When the printing machine power is switched on, the power on reset automatically sets the gate output signal low, holding the gate solenoids de-energised. The gate 60 is then down ready to brake and control the first sheet of paper 50 that approaches. If a paper sensor (not shown) at the gate 60 sees no paper, the gate 60 will remain down. When the pauper sensor detects a sheet of paper 50 approaching the gate 60, the gate control logic circuits are enabled. Immediately the logic- looks for its index pulse. As soon as this is received, the gate pulse count is loaded from the setting of the rotary switches into -the gate count register. The encoder Channel A pulses the decrement at a rate of two counts per pulse. As soon as the counter reaches zero, the gate output signal goes high and the gate lifts.This allows the paper 50 to advance up to the head lay device 64 where it is once again stopped. As soon as the head lay device 64 lifts, the sheet of paper 50 is released into the gripping fingers 80 of the gripper means 78 and then the sheet of paper 50 is taken away for printing. As long as that sheet of paper is passing the paper sensor, the gate 60 remains up. As soon as the sheet of paper 50 has passed through the gate 60 and the detector sees no paper 50, the logic circuits de-energise the gate solenoids, enabling the gate 60 to drop and process the next sheet of paper 50. When the head lay/ gate overide switch is activated, the logic commands are overidden and the gate 60 is lifted, as it will if the printing machine 2 is reversed. In a shut down condition, the logic commands are overidden and the gate 60 stays shut stopping any further sheets of paper 50 on a feeder for the printing machine 2 entering the printing machine 2.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, the logic circuit shown in Figure 3 with its self explanatory wording may be varied if desired.

Claims (11)

1. A printing machine having a gate for sequentially passing sheets of paper through the printing machine, and a head lay device for engaging a front edge portion of the sheets of paper to cause them to lay correctly before they are printed by the printing machine.

2. A printing machine according to Claim 1 in which the gate has a shoulder portion against which the sheets of paper abut.

3. A printing machine according to claim 1 or claim 2 in which the head lay device is able to advance or retard the sheets of paper in relation to an impression roller which forms a part of the printing machine.

4. A printing machine according to claim 3 and including a stepper motor arrangement for advancing or retarding the sheets of paper in relation to the impression roller.

5. A printing machine according to any one of the preceding claims in which the head lay device comprises a pivotable bar and a plurality of fingers which extend from the bar, the printing machine being such that the fingers move in and out of a series of complementary recesses in an impression cylinder of the printing machine as the bar pivots backwards and forwards.

6. A printing machine according to any one of the preceding claims and including a pair of side adjustor devices for adjusting the sides of the sheet of paper for assisting in laying the sheets of paper correctly before they are printed by the printing machine.

7. A printing machine according to claim 6 in which the side adjustor devices are a pair of reciprocating devices which repeatedly knock against the sides of the sheet of the paper.

8. A printing machine according to claim 7 in which the side adjustor devices operate via a cam and a lever arrangement.

9. A printing machine according to any one of the preceding claims and including electronic control means for controlling the time at which the head lay device releases the individual sheets of paper to allow them to be gripped by gripper means which forms part of the printing machine and which pulls the individual sheets of paper through the gate and the head lap device for printing.

10. A printing machine according to claim 9 in which the electronic control means comprises a visual aid for assisting an operator to set up the printing machine such that the head lay device correctly releases in relation to the time the gripper means operates to grip the individual sheets of paper, the visual aid comprising a pair of lights which are arranged to operate together when the head lay device and the gripper means are correctly synchronised, one of the lights being provided on a paper position sensor device and the other light being provided on a control panel of the machine.

11. A printing machine substantially as herein described with reference to the accompanying drawings.