GB2198265A

GB2198265A - Web feed apparatus with registration means

Info

Publication number: GB2198265A
Application number: GB08624652A
Authority: GB
Inventors: Burkhard Wilfred Wetzel
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-14
Filing date: 1986-10-14
Publication date: 1988-06-08
Anticipated expiration: 2006-10-14
Also published as: GB8624652D0; GB2198265B

Abstract

Web feed apparatus suitable, for example, for use in printing on the reverse face of photographic paper, comprises a rotary drive member (11) in the form of a drum with a counter roller (14) for driving a web (15) continuously from a delivery roll (15) to a take up roll (25) thereof. The rotary drive member may be a print drum having a printing plate (12) thereon with a recess (13) positioned so that at least once during each revolution of the print drum (11) the web (15) is disengaged from the print rolls (12, 14) to allow corrective motion to be applied by correction drive rollers (23, 24), this movement being permitted by the presence of loops (20, 29) on rollers (18, 19, 27, 28). A mark reader (32, 33) provides an indication of the arrival of the web (15) in a predetermined position, whilst an angular position sensor (40) provides a continuously updated indication of the angular orientation of the main drive drum (11). A CPU calculates any correction necessary to ensure registration and energises a stepping motor to drive the rollers (23, 24). <IMAGE>

Description

Web Feed Apparatus with Registration Means The present invention relates generally to web feed apparatus, and particularly to web feed apparatus having means for ensuring registration between the web and a treatment device of the apparatus.

A requirement for feeding web or web like material is encountered in many fields of activity, notably the printing industry where it is convenient to store the stock material on which images are to be formed in rolls of continuous web to be passed between rotary drive and print rollers for applying successive images. Accurate synchronisation of successive print rollers is essential in order to ensure that successive images are in register with one another, and this is of particular importance when colour printing since successive images of different colours are applied in separate operations.

Another situation when it is convenient to print on continuous web-form stock material occurs in the photographic industry where, although individual photographic images are produced by exposure of individual frames, processing of the material is more convenient in web form. This is particularly true with the currently popular 35 mm photographic film since individual images on the film are too small to separate from the strip of film exposed in a camera. Similarly, there are many circumstances when the so-called "contact" prints are required, and these are usually formed on continuous web with the images from a plurality of strips of negative film. In this way, long rolls of web bearing a large number of individual photographic images are formed.If it is desired to print information relating to the photographic images, for example, identifying the source, or even with blank information tables to be filled in individually, it is necessary to ensure registration of the printing on the reverse of the photographic paper with the images on the front face. These images are not all regularly spaced, however, because of the differences in the cameras originally exposing the photographic film, as well as other variations which occur during the processing of the film, and for accurate registration it is necessary to be able to identify a fixed point between adjacent photographic images. Currently, this is achieved by putting separator marks between adjacent photographic images, these usually being provided either in the form of a photographic colour spot on the edge of the strip, or by carbon print mark on the reverse face of the strip.Alternatively, a small hole may be punched in the gap between adjacent photographic images. Printing on the reverse face of the photographic paper can then be effected by registering the print equipment with such index marks during printing. Registration involves releasing the drive pressure between cooperating rolls, however, in order to effect adjustments to the longitudinal position of the web or strip with respect to the print rolls, and this is a slow, time consuming and therefore expensive process.

The present invention seeks to provide web feed apparatus in which there are provided means for automatically adjusting the position of the web longitudinally of its path with respect to the angular position of a rotary drive member such as a print drum, whereby to enable continuous web feed printing to take place.

According to one aspect of the present invention, therefore, web feed apparatus having means for ensuring registration between linearly spaced indicator marks on a web and a treatment device (such as a printing machine or the like) comprises a primary rotary drive member of the apparatus, rotation of which drives the web, the rotary drive member having a recess in its surface such that at least once during each revolution of the rotary drive member the web is disengaged therefrom, means for detecting the presence of an indicator mark on the web at a detection location, and corrective drive means operable, when the recess in the main drive roller is in register with the web, to cause relative forward or backward movement of the web with respect to the rotary drive member whereby to bring the web into registration with the said index position defined by the mark.

Appropriate linear movements of the web can be effected by driving corrective feed rollers which are constantly in contact with the web, and which rotate at a constant speed when the main rotary drive member is in contact with the web, and which are driven to rotate in one direction or another by appropriately indexed angular movements in order to effect correction of the relative positions of the rotary drive member and the web. It will be appreciated that if the rotary drive member is continuously driven then relative backward movement of the web can be effected merely by slowing the drive to the corrective feed rollers without it being necessary for these actually to be displaced in a reverse direction.

According to another aspect the invention comprises web treatment apparatus having a rotary drive member and means for treating successive areas of the web spaced along the length thereof in which there are provided means for detecting registration indicia on the web, means for determining the angular orientation of the rotary drive member, and means by which the rotary drive member may be periodically released from engagement with the web, whereby to permit corrective movements of the web to be effected by corrective drive means with respect to the rotary drive member.

Such release of the rotary drive member may be effected, as discussed above, by the provision of a recess in the rotary drive member, or may alternatively be achieved by a periodic release of drive pressure from a counter roller enabling relative movement between the rotary drive member and the web to take place.

In a preferred embodiment of the invention the rotary drive member is a photographic print drum and the web is photographic paper with photographic images printed on one side, the print drum being operative to print on the reverse face of the photographic paper.

Preferably, the means sensitive to the orientation of the rotary drive member is a photo sensor positioned in the path of an associated indicator on the rotary drive member. Such indicator may be a reflective strip, an notch or other means for producing an output signal representative of the position of the print drum.

In a system for the treatment of web according to the invention, it is preferable to form the web into loops on either side of the rotary drive member to permit the corrective drive movements to be effected without disturbing feed or take up rolls of the web.

Preferably, the corrective drive is effected by a micro processor which determines the required advancement of the web whilst the rotary drive member is disengaged therefrom, to position the web in a predeterminable longitudinal position. Preferably the predeterminable longitudinal position is determined by a mark or series of marks on the web and a mark reader positioned such that after the passage of each photographic image the index mark associated therewith will be located to a given side of the mark reader so that, in normal circumstances, the machine will always operate to adjust the longitudinal position of the web in a given direction. In this respect, the reading of the mark by the mark reader determines that the web is in a known position, and this is then adjusted in dependence on the sensed angular position of the rotary drive member. The drive to the rotary drive member is constant. It is therefore necessary to have a continuously updated check on the angular position of the rotary drive member whereby to adapt the position of the web to obtain a predetermined relative position between the web and the rotary drive member.

One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of the embodi ment; and; Figure 2 is a block diagram illustrating the organisation of the electrical control units.

Referring first to Figure 1 there is shown a print drum, generally indicated 11, having a printing plate 12 over a part of its surface and a recess 13 occupying the remainder of the circumference. A rubber coated counter roller 14 cooperates with the print roller 11 in printing and transporting a web 15 which, in this embodiment, is a web of photographic paper having photographic images already printed on one face (the lower face as viewed in Figure 1) so that the printing drum 11 operates to print information on the reverse face of the web.

The web 15 is carried to the print drum 11 from a supply roll 16 of photographic paper driven by a feed motor schematically indicated 17. The web 15 passes over two loop rollers 18,19 which act to form an open loop 20 of the web 15, and the size of the web, between maximum and minimum acceptable sizes, is determined by loop sensors 21,22. From the loop roller 19 the web 15 passes between two corrective drive rolls 23, 24 the operation of which will be described in more detail below. As the web 15 passes between the print drum 11 and the counter roller 14 an image is aplied thereto by the print plate 12 which is inked by an inking system comprising inking rollers 35,37 and an ink bath 36 of otherwise conventional type known for web offset printing.

After printing the web 15 is rewound into a coil 25 by a rewind motor 26 schematically illustrated in Figure 1 which acts continuously to draw the web 15 from a loop 29 thereof formed between the print drum 11 and the take-up coil 25. The loop 29 is formed by passing the web 15 over two loop rollers 27,28 and the size of the loop is detected by sensors 30,31. Control of the size of the loops 29 and 20 is effected to maintain them within the limits determined by the sensors 21,22 and 30,31 in a manner which will be described in more detail below.

Between the print drum 11 and the take-up loop 29 there are located a light source 32 and light cell 33 of an optical mark reader, and an ink drier 34 illustrated only schematically in Figure 1.

Finally, the angular position of the print drum 11 is determined by a photo detector 40 which is sensitive to a suitably shaped index mark 38 having a notch 39 corresponding to the recess 13. The photo detector 40 may be one incorporating its own light source, and it acts to produce a signal indicating when the recess 13 is in register with the nip between the print drum 11 and the counter roller 14. The index 38 may be adjustable in order to synchronise the signals from the photo detector 40 with the position of the print drum 11.

Turning now to Figure 2, the electrical control is effected by a central processor unit 48 receiving signals from input ports 52 supplied on lines A and B with signals from the print drum angular position sensor 40 and the optical mark reader 32,33. The central processor unit 48 also receives input signals from the loop sensors 21,22, on lines C and D and from loop sensors 30,31 on lines E and F.

The input to the processor unit 48 is also supplied via an input port 54 with signals representing a selected corrective feed movement which is determined by the setting of an analogue switch 55 having four selectable segments the first three of which determine the number of steps to be taken in the corective feed and the last of which determines the direction. This latter switch segment will, naturally, only be selected between one of two values.

An eprom 49 stores the control programme for the central processor unit 48 which issues control signals on three output lines via the output ports 46, 47 and 50. The outport port 46 delivers the signals on three lines, two of which operate to control the power supply to the feed motor 17 and the feed motor 26 of the feed roll and rewind roll respectively, and also via a line 42 controls an on/off switch for the print drum motor (not shown). The output port 47 delivers signals to a stepper motor control unit 44 which controls the movement of a stepping motor 41 which drives the corrective drive rolls 23,24. Finally the output port 50 drives a set of fault-indicating light emitting diodes 51 as will be described below.

In operation of the apparatus described above, the print drum 11 is continuously rotated to print the reverse face of the web 15 with the loops 20 and 29 being maintained with predetermined limits set by the positions of the loop sensors 21,22 and 30, 31. When, for example, the loop 20 has reached its maximum size, as illustrated in Figure 1, the proximity of the loop fundus is detected by the sensor 22 to provide an input signal to the central processor unit 48. This produces an output signal to the output port 46 acting to de-energise the feed motor 17. Continued rotation of the print drum 11 and counter roller 14 draws web 13 from the loop 20 causing this to reduce in size until the sensor 21 produces a signal indicating that the loop is no longer present. This is then processed through the central processor unit 48 to produce a signal switching on the feed motor 17 again.In this way the loop 20 continuously varies between its maximum and minimum size whilst the section of the web 15 between the two loops 20, 29 can be moved freely in one direction or the other without affecting the feed motor 17 or the rewind motor 26.

Once during each revolution of the print drum 11 the recess 13 comes into register with the counter roller 14, at which time the web 15 is no longer trapped between them and can be moved longitudinally to adjust its position relative to the angular position of the print drum. The web 15 is, in fact, still driven by the rotation of the corrective drive roll 23,24 which normally turn in synchronism with the rotation of the print drum 11. The web 15 has a plurality of index marks along its length, each mark being positioned between adjacent photographic images formed on the under face of the web 15, and when such a mark is detected by the optical mark reader 32,33 this issues a signal which is supplied via input line B to the input port 52 of the processor unit 48.At the same time the photo detector 40 produces an indication of the angular position of the print drum 11 and the processor unit 48 then acts to determine the number of steps, in one direction or the other, necessary to bring the web 15 into a predetermined relative position with respect to the print drum 11. The stepping motor 41 is thus energised by a number of steps determined by the processor unit 48, and controlled via the output port 47 and the stepper motor control unit 44 to drive the corrective drive rolls 23,24 by a number of index increments to bring the web 15 into the correct registration position.This is necessary because the images positioned along the photographic paper constituting the web 15 are not equally and regularly spaced so that individual corrective movements are required for each image in order accurately to register the printing on the reverse face with the image on the front face. The position of the optical mark reader 33 is adjustable and is set normally so that each index mark is to the right of the mark recorder when the recess 13 first comes into register with the counter roller 14. Immediately this occurs the corrective drive then starts to advance the paper forward until the mark reaches the optical mark recorder 32,33. The corrective drive then advances forwards or backwards a number of steps determined by the setting of the switch 55 in order to bring the web 15 into the required longitudinal position. If, because of a variation in the image positions, the corrective drive movements take longer than the "window" during which the recess 13 is in register with the counter roller 14, so that the micro processor detects that the print drum has advanced again to its engaged position before the corrective drive has completed its movements, then a signal via the output port 50 to one of the light emitting diodes 51 indicates the fault and the line 42 is energised to switch off the print drum motor enabling manual correction to be effected before the apparatus is again put into operation.

Claims

1. Web feed apparatus having means for ensuring registration between linearly spaced indicator marks on a web and a treatment device such as a printing machine or the like, comprising a primary rotary drive member of the apparatus, rotation of which drives the web, the rotary drive member having at least one recess in its surface such that at least once during each revolution of the rotary drive member the web is disengaged therefrom, means for detecting the presence of an indicator mark on the web at a detection location, and corrective drive means operable, when the or a recess in the main drive roller is in register with the web, to cause relative forward to backward movement of the web with respect to the rotary drive member whereby to bring the web into registration with the said index position defined by the mark.

2. Web treatment apparatus having a rotary drive member and means for treating successive areas of the web spaced along the length thereof, in which there are provided means for detecting registration indicia on the web, means for determining the angular orientation of the rotary drive member, and means by which the rotary drive member is periodically released from engagement with the web whereby to permit corrective movements of the web to be effected by corrective drive means with respect to the rotary drive member.

3. Web feed apparatus as claimed in Claim 1 or Claim 2, in which the rotary drive member is a photographic print drum and the web is a photographic strip.

4. Web feed apparatus as claimed in any of Claims 1 to 3, in which the means sensitive to the orientation of the rotary drive member is a photo sensor with an associated index mark on the drive member.

5. Web feed apparatus as claimed in any of Claims 1 to 4, in which the web is held in the apparatus with open loops on either side of the rotary drive member whereby to permit the corrective drive movements to be effected without disturbing feed or takeup rools on either end of the web.

6. Web feed apparatus as claimed in any of Claims 1 to 5, in which the corrective drive is effected under the control of a micro processor operating to cause the web to advance when the recess is in register with the web, such movement continuing until an index mark arrives at a mark reader.

7. Web feed apparatus as claimed in Claim 5, in which the mark reader is positioned in such a way that the index mark is always located to a predetermined side thereof such that advancing movements in a predetermined direction will always result in displacement of the mark into register with the mark reader.

8. Web feed apparatus as claimed in Claim 6 or Claim 7, wherein the corrective drive is controlled to drive the web by a predetermined further distance to a given registration position after the arrival of a mark at the mark reader is detected.

9. Web feed apparatus as claimed in any of Claims 6 to 8, in which there are further provided means for continuously monitoring the angular position of the rotary drive member whereby to provide an indication of its angular orientation upon arrival of a mark at the said mark reader.

10. Web feed apparatus as claimed in any preceding Claim, wherein there are further provided means for generating a fault indication if the rotary drive member re-engages with the web before the corrective drive movement has been completed.

11. Web feed apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.