Printing in register on sheets

Information

  • Patent Grant
  • 4552065
  • Patent Number
    4,552,065
  • Date Filed
    Monday, September 17, 1984
    40 years ago
  • Date Issued
    Tuesday, November 12, 1985
    39 years ago
Abstract
This invention is concerned with the high speed printing of a line of text on a sheet in very accurate registration with an edge of the sheet or another feature (for example an existing print line) on the sheet. The sheet is fed without preregistration on to a track (10, FIG. 1) which passes the printing station (20). A detector (16) adjacent the track senses the arrival of the edge or some other feature of the sheet and a printing control means (14) responsive to the detector signal initiates the firing of the printing hammer (22) when the print line reaches the printing station, a registered operation being thereby effected without stopping the sheet. The detector signal may start the operation of a counter (70, FIG. 4) and a firing signal is sent to the hammer control circuit (100, 102, 104) when the count reaches a value dependent on the distance between the detector and the point at which the printing operation takes place and (unless the new print is to be in alignment with a detected print line) also dependent on the distance on the sheet between the edge or feature detected and the position at which the new print is to appear.
Description
Claims
  • 1. Apparatus for printing a line of characters in a desired print line location on each of a series of sheets so that the resulting printed line of each sheet is registered with respect to a feature of the sheet, comprising:
  • means defining a flow path for the sheets;
  • a printing station located at a predetermined point along the flow path and comprising impact printing means including individually rotatably adjustable print wheels mounted on a common shaft, the axis of which is transverse and fixed with respect to said flow path, each print wheel having a plurality of character faces spaced around its periphery and individually selectable by rotation of each wheel about the said axis to predetermined print positions, the said axis extending in a direction parallel to the required line of characters on the sheet passing through the apparatus, and a hammer to cause impact printing of a sheet against a type face whereby the print wheels together print a line of characters, one for each wheel, in a single operation, each character printed being determined by the respective rotated position of the corresponding print wheel;
  • means for locking the print wheels in the positions to which they have been rotated;
  • sheet feeding means for feeding a succession of sheets the spacing between which may vary, continuously and at a substantially constant speed along the flow path and through the printing station,
  • sensing means detecting the arrival of the said feature of the sheet at a given point along the flow path and providing a corresponding electric signal; and
  • printing control means responsive to said signal from said sensing means and to the speed of travel of the sheet to initiate printing hammer firing when the desired print line location on the sheet reaches the printing station, whereby regardless of the speed of travel of, intervals between the individual sheets, or time of arrival of the sheets at the printing station, printing of a line of characters is effected by the stationary print wheels in register with respect to the said feature of the sheet without substantially changing the speed of the sheets.
  • 2. Apparatus in accordance with claim 1, comprising a spring for the printing hammer, a cam for driving the hammer against the spring and which maintains the hammer against the spring until printing is initiated, and means for driving the cam to its hammer release position, allowing the spring to throw the hammer towards the print wheels;
  • the apparatus further including a stop which is hit by the hammer when the hammer reaches the point of printing.
  • 3. Apparatus in accordance with claim 1, in which the printing control means includes:
  • a first counter, the operation of which is initiated by the signal from the detection means;
  • a circuit which initiates printer hammer firing when the counter reaches a predetermined count; and
  • a pulse generator supplying the counter with clock pulses at a rate corresponding to the speed of movement of the sheet along the flow path.
  • 4. Apparatus in accordance with claim 3, in which the detecting means provides a first signal in response to the detection of the edge of a sheet and a second signal responsive to the detection of an existing mark on the sheet, the apparatus comprising:
  • a second counter connected to receive the first and second signals; and
  • a comparator;
  • the first signal initiating counting in the second counter and the second signal applying the contents of the second counter, representing the distance between the said edge and the existing mark, to the comparator means to determine whether the said distance lies within a predetermined range; and wherein the second signal additionally initiates counting in the first counter.
  • 5. Apparatus in accordance with claim 3 or 4, including:
  • means for preloading the first counter with a value dependent on both the distance between the detector and the point along the flow path at which the printing operation takes place, and the distance on the sheet between the feature detected and the printing line location on the sheet; and
  • in which the first counter counts clock pulses, starting from the sensing of the said feature by the detecting means, and initiates printing hammer firing when the count reaches the preloaded value.
  • 6. Apparatus in accordance with claim 3, in which the pulse generator includes a shaft encoder coupled to a shaft for driving a belt on which the sheet is advanced along the flow line to the printing station, for providing the said clock pulses.
Priority Claims (2)
Number Date Country Kind
8125048 Aug 1981 GBX
8206220 Mar 1982 GBX
Parent Case Info

This application is a continuation of application Ser. No. 408,435, filed Aug. 16, 1982, now abandoned. This invention is concerned with performing a printing operation on a sheet in accurate register with an edge of the sheet, or with an earlier operation performed on the sheet, for example an earlier printing, slitting, perforating or drilling operation. In many cases, marks must be printed on a sheet in very accurate register with the edge or earlier operation. An example is the printing of personalising information on individual cheques or sheets of cheques for machine reading. Such personalising information may be printed by more than one printing unit. An individual cheque printed with personalising information will be bound with other cheques to make up a cheque book and a sheet of cheques so printed will subsequently be guillotined, after which the individual cheques from a number of sheets will be formed into individual cheque books. Thereafter, that part of the personalising information which is printed with magnetic ink will be read by a machine and any error in register of the printed information will affect the ability of the machine to make an accurate reading. Apparatus according to the present invention, for printing on each of a series of sheets so that the resulting printed mark on a sheet is registered with respect to an edge of the sheet or with respect to an operation previously performed on the sheet, comprises: means defining a flow path for the sheets; a printing station located at a predetermined point along the flow path and including type faces and a hammer or hammers to cause impact printing of a sheet against the type faces; and further comprises sheet-feeding means feeding each sheet continuously along the flow path and past the said station; sensing means detecting the arrival of the edge of the sheet, or the arrival of a feature resulting from the said previous operation on the sheet, at a given point along the flow path and providing a corresponding electric signal; and printing control means responsive to the signal from the detecting means to initiate the firing of the printing hammer or hammers when the print line reaches the printing station whereby a registered printing operation is effected without stopping the sheet. In the preferred apparatus embodying the invention, the sensing means is located upstream of the printing station. In this preferred form, the printing control means comprises timing means controlled in accordance with the distance of the portion of the sheet to be printed from the printing station at the moment of detection, to initiate the firing of the printing hammer or hammers after an interval equal to the time required to advance the sheet through that distance. The interval defined by the timing means takes into account the speed of movement of the sheet feeding means. The timing means may, for example, respond to clock pulses provided by a shaft encoder coupled to a shaft for driving a belt on which the sheet is advanced along the flow line to the printing station. In the past, when very accurate register was required, it was customary to feed the sheets along a track towards the printing station using a gripper transport system, pinch rollers or a vacuum track, for example. The sheets were fed on to the track in accurate register or were registered immediately after being fed on to the track. Alternatively, the sheets were registered at the printing station by stopping the track or the sheets. In such cases, the apparatus operates in predetermined cycles and the cycle length must be reset each time the size of the sheet is changed and each time the positions of the personalising indicia are changed. Machines for carrying out such operations generally require the stations which perform printing or other operations on the sheet to operate synchronously with one another and with the track, each time the sheet transport mechanism (or the sheet) is arrested. This requires complex timing controls interlinking all the operations. Machines of this kind are described in our British patent specifications Nos. 1214639 and 2016377A. In all instances of impact printing of high quality code lines of which we are aware, the sheet has been held stationary for the printing operation. Apparatus embodying the present invention avoids the requirement for a stop to arrest the movement of the sheet to ensure that the printing is performed in registered condition, and also makes it unnecessary to ensure that the sheet is registered in relation to an operating cycle of the printing station before the sheet reaches that station Printing on a moving sheet is not new in itself. Conventional printing machines, using offset litho or letterpress, for example, print on a moving sheet or web. However, the printing plate is also moving in relationship with the sheet. Numbering machines may also employ a numbering box mounted in a chase, again moving in relation with the sheet. It has previously been considered that any attempt to print a code line using a stationary numbering unit with a continuously moving sheet would be unsatisfactory, in particular that the positioning of the code line on the sheet would not be sufficiently accurate. By making advance registration of the sheet unnecessary, the invention removes the design constraint of synchronised track and printing station and the need for mechanical registration means. Furthermore, operation of the print wheels and other components of the printing station are triggered only when a sheet arrives at the station, so that wear on these components is reduced. In addition, the invention allows the track to be split into sections of different lengths, if desired, and allows different speeds for different operations, as the requirement for a timed relationship between the operations is removed; indeed, a portion of the track or the sheet may be stopped for some operations. Slight variation in speed between track sections will not lead to registration problems and the mechanical strain imposed by the continual stopping and starting of the track is also avoided. Unregistered and untimed sheets may be fed from a low-cost sheet feeder or directly from a printing machine, for example a litho printing machine which may be used to print the non-variable information. In the preferred embodiment of the invention, the means responsive to the resulting signal from the detecting means includes a counter, the operation of which is initiated by the signal from the detecting means, and a circuit which initiates the performance of the printing operation on the sheet when the counter reaches a predetermined count, the apparatus further including a pulse generator supplying the counter with clock pulses at a rate corresponding to the speed of movement of the sheet along the flow path. This apparatus further checks the position of an existing mark, for example a part-printed code line. For this purpose, the detecting means provides a first signal in response to the detection of the edge of a sheet and a second signal responsive to the detection of an existing mark on the sheet, the first signal initiating counting in a second counter and the second signal being used to cause the contents of the second counter, representing the distance between the said edge and the mark, to be applied to comparator means for determining whether the said distance lies within a predetermined range. The printing operation is carried out by means of a hammer driven against a spring by a cam and thereafter released to allow the spring to throw the hammer towards a print wheel, the apparatus further including a stop which is hit by the hammer when the hammer reaches the point of printing. The period of contact may be less than one millisecond and for this brief interval it appears that in the embodiment of the invention to be described there is a local stretching of the cheque paper in the contact area; it is to be understood that the statement that the sheet is fed continuously past the station includes such a case, which is to be distinguished from prior arrangements in which the sheet was stopped prior to the printing operation. The detector may be responsive to electromagnetic radiation (for example, an infra-red detector) or a capacitive, ultrasonic or inductive detector; alternatively, where only the edge of the sheet need be sensed, the detector may be a microswitch or a simple reflective, or see-through detector. Such detectors are commercially available and their construction is well-known. The detector may be a simple photodell but may also be of the type employed for reading bar codes or 0.C.R. characters. If desired, a further detector may be included so arranged that the sheet can be checked for skew, any resulting skew signal being used either to cause a further side lay operation or the rejection of the skewed sheet from the system.

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3049990 Brown et al. Aug 1962
3191526 Ross Jun 1965
3254596 Shoup et al. Jun 1966
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Foreign Referenced Citations (1)
Number Date Country
2648870 May 1978 DEX
Continuations (1)
Number Date Country
Parent 408435 Aug 1982