[0001] This invention relates to a printer arranged to print a unique sequence of characters
on each of a number of forms fed one at a time along a path, and in particular - but
not exclusively - relates to such a printer arranged to operate at relatively high
speeds. The invention further relates to methods of printing forms.
[0002] Not infrequently, it is required to print a relatively large number of similar pieces
of paper (each of which is herein referred to as a 'form'), the printing differing
only in that each form carries a printed sequence of characters unique to that form.
For example, tickets for all manner of occasions and functions, lottery tickets, bank
account cheques, travellers cheques and bank notes all contain certain data unique
to each printed form, all of the remaining print detail on a given print run being
identical. The increasing use of computers and computer printers such as laser printers
allows the production of such forms in an economic manner, but for certain types of
security printing, the print quality or type produced by such printers is not considered
adequate. For these operations, the printing must be performed by a conventional letter
press printing operation, where a wet ink is pressed into the surface fibres of the
paper.
[0003] In order to allow adequate productivity for security items such as travellers cheques
and bank notes, it is conventional to print relatively large sheets one at a time,
each sheet bearing an array of the forms. Typically, each sheet is first printed by
an offset printing process, and then further printed by means of an intaglio printing
process, which two printing processes substantially complete each form on the sheet
except for the printing of the individual numbers or other characters thereon. Each
sheet is then subjected to a letter press printing process, in which a large chase
of numbering machines pre-set as required is used to print unique numbers on all of
the forms on one sheet, in one impression. Simultaneously, a facsimile signature may
also be printed on each form at that time. Following the numbering printing step,
a stack of printed sheets is cut up so as to separate all of the individual forms,
which forms are then inspected as a part of a quality control process.
[0004] The above described process suffers from the disadvantage that the setting up of
the chase of numbering machines takes a most considerable time, leading to a great
reduction in productivity, especially if only relatively short print runs are required.
The mechanical complexity of all of the numbering machines adds to unreliability,
giving an increased number of reject forms. There is moreover the difficulty that
should the numbering or character sequence employed be required to be continuous throughout
the print run, any rejected forms must subsequently be made up by special, one-off
print runs with a numbering machine set expressly to the number of a rejected form.
This process in itself is extremely slow and inefficient to operate.
[0005] It is a principal aim of the present invention to provide a printer arranged to overcome
the disadvantages of the known printing process as described above, in order to allow
the production of a number of forms in one print run with each form carrying a unique
sequence of characters. It is a further aim of this invention to provide a method
for printing such forms which method at least mitigates the disadvantages of the known
process, as discussed above.
[0006] Accordingly, one aspect of the present invention provides a printer arranged to print
a unique sequence of characters on each of a number of forms fed one at a time along
a print path, which printer has a plurality of print stations spaced along the print
path, characterised in that each print station is adapted to print one digit on a
form fed along the print path whereby the unique sequence of characters is built up
by a plurality of printing operations on the form as the form advances along the path,
each print station being adapted to print any one of a number of different characters
and there being means arranged to permit the selective change of the printed character
between each form printing operation.
[0007] As compared to the usual printing process discussed above for the security printing
of forms such as travellers cheques and bank notes, which is essentially a batch process
simultaneously producing a number of finished forms on one large sheet which sheet
is subsequently divided up to yield the individual forms, the printer of the present
invention operates essentially in a serial manner where the pre-printed forms are
fed one at a time through the printer for the numbering operation. In the prior art
method, the unique numbers or other characters on any one form are all printed simultaneously;
with the printer of the present invention each character of the unique sequence of
characters is printed one at a time, so that the overall sequence is being built up
as the form advances through the printer. This leads to several significant advantages:
the setting up time for a given unique number may be very small as compared to the
prior art printers and may easily be computer-controlled, and the forms may be inspected
for quality control prior to being printed with a unique character sequence so leading
to only very small numbers of rejected numbered forms. In turn, this largely eliminates
the problem of making-up the numbering sequence. A further advantage is that by having
a number of essentially similar print stations, the printer may be relatively simple
and so expensive to construct.
[0008] According to a second aspect of the present invention, there is provided a method
of printing a number of forms each of which carries a unique sequence of characters,
in which method a number of pre-printed forms are produced and then fed one at a time
through a printer having a plurality of print stations, which method is characterised
by the printing on each form one character of the unique sequence at each print station,
and changing the printed character at least at one print station between each form-printing
operation.
[0009] The unique sequence of characters printed on each form may be a simple numerically
advancing-sequence of digits, or may consist of alpha-numeric characters which are
altered as appropriate between each form printing operation, to ensure that each form
contains a unique sequence.
[0010] The printer may include a further print station at which at least one static character
or group of characters is printed on each form, which static character or group of
characters remains constant for the duration of a print run. For example, a typical
bank note may carry a unique sequence of characters consisting of a first static field
of three alpha-numeric characters, followed by a field of seven numeric characters,
the count of that field being advanced by one unit for each form printing operation.
[0011] It is preferred for each print station employed in a printer of the present invention
to have a print roll defining with a pressure roll a nip through which each form to
be printed is passed, the print roll including a print head carrying a number of distinct
indicia, such as the digits 0-9. Each print station advantageously is arranged such
that during printing of one form the print roll turns through less than one full turn,
the print head at any one station being advanced following the printing of a form
if the character next to be printed at that station is to be different from the previous
character. Such selective advance of the print head may be performed by any suitable
mechanism, such as a ratchet and pawl mechanism controlled electro-mechanically,
or by a direct acting electro-mechanical mechanism. Conveniently, the print head may
be in the form of a character wheel.
[0012] For the arrangement as described above, the print roll at each print station should
be operated in synchronism with the print rolls at the other print stations and also
in synchronism with the feeding of a form through the printer. In this way, the printing
of each character at precisely the required position on a form may be assured, so
as properly to build up the required unique sequence of characters. Conveniently therefore,
all of the print rolls may be mechanically coupled together for simultaneous synchronous
rotation, a synchronised paper feed arrangement also being provided to ensure the
feeding of a form into the printer at the correct moment.
[0013] In the preferred form of printer of this invention as described above, it is advantageous
for there to be means to withdraw the pressure rolls out of contact with the associated
print rolls, in the event that no form is fed through the printer during the operation.
In this way, the false printing of a character on to the pressure roll may be avoided.
Similarly, it is preferred for there to be means to relieve the inking of the print
head in the event that no form is fed through the printer.
[0014] The printer of this invention advantageously is provided with an input hopper from
which the forms may be drawn one at a time for printing, the hopper being provided
with known mechanisms to extract forms one at a time therefrom and to feed such forms
through the printer in a timed relation to the operation of the print rolls. Following
the completion of printing, the printed forms may be deposited in an output hopper
for such further processing as may be required.
[0015] By way of example only, one specific embodiment of printer of this invention and
operating in accordance with a method of this invention will now be described in detail,
reference being made to the accompanying drawings, in which:-
Figure 1 is a diagrammatic side view of the printer of this invention;
Figure 2 is a diagrammatic detail view on part of one print station of the printer
of Figure 1; and
Figure 3 is a side view on the detail of Figure 2.
[0016] In the drawings, there is shown an input hopper 10 for storing a stack of forms 11
to be printed, the hopper 10 being provided with an exit gate 12 and extraction rollers
13, to feed forms one at a time into a feed roller nip 14, controlled by a solenoid
15. The detection of the leading edge of a fed form is performed by a photoelectric
detector 16.
[0017] The forms are advanced along a print path 17 by a plurality of drive rolls 18, the
print path 17 extending through a number - and typically 7 - print stations 19, only
three of which are shown in Figure 1. An output hopper 20 collects printed forms,
from where the forms may be removed for further processing, as required. A gate 21
may be provided to deflect mis-fed forms into an error bin 22.
[0018] Each print station comprises a print roll 23 and a pressure roll 24 loaded by a spring
25 and having a solenoid 26 to effect the withdrawal thereof. Incorporated within
the print roll 23 is a print head comprising a wheel 27 having a plurality of characters
- such as the numbers 0-9 - formed around the periphery thereof, a suitable mechanism
being provided selectively to advance the character of the print wheel 27 which will
be printed upon rotation of the print roll 23. An inking mechanism including rolls
28, 29 and 30 is arranged to ink the wheel 27, a withdrawal mechanism (not shown)
being provided for inking roll 28, to vary the pressure of that roll, or to lift that
roll clear of the wheel 27.
[0019] The advancing mechanism for each print wheel 27 includes a cam 31 controlled by a
solenoid 32 mounted on a fixed part of the printer. The print roll carries a cam follower
33 pivoted on pin 34 mounted on roll 23 and having a pawl 35 which operates on a ratchet
wheel 37 connected to the print wheel 27. A further pawl 36 is pivoted on pin 34 and
also operates on ratchet wheel 37, and suitable springs (not shown) are provided to
urge the cam follower and pawls in the appropriate senses. The operation of all of
the solenoids 32, controlling the advancement of the various print wheels 27, preferably
is effected by a computer, which selects the required unique number for printing on
each form. Each print wheel may be advanced one step on each rotation of the corresponding
print roll, depending upon the setting of the cam 31, and so any desired number may
be generated by rotating all of the print rolls a maximum of ten turns.
[0020] The actual position of each print wheel 27 may be detected by means of a magnet 38
mounted on the print wheel and operating in conjunction with a suitable sensor (not
shown).
[0021] Once the first required number sequence has been set up, thereafter no print wheel
27 is required to advance more than one step between printing operations. Typically,
the print wheel at the first print station 19 would be advanced one step for each
form, the print wheel at the second print station would be advanced on every tenth
form, the print wheel at the third print station every hundredth form, and so on.
[0022] A final print station (not shown) may be arranged at the end of the print path 17,
which final station may include a printing plate which prints the same static characters
on every form. The printing plate should be removable for replacement by some other
plate, as appropriate for any given printing run.
[0023] It will be appreciated that using the printer as described above, variable character
sequences may be printed on forms, with the character sequence being built up along
the array of printing stations. Provided that the operation of all the print stations
is properly synchronised and the feeding of the forms along the print path is correspondingly
controlled, the required character sequences may properly be built up as a form advances
along the print path, with all the characters correctly aligned and in the required
relative disposition, one with respect to the others.
[0024] The printer as described above is relatively simple and so may operate at relatively
high speeds, printing on the fly the characters on the forms as the latter are fed
along the print path. Typically, therefore, about ten forms per second may be printed;
if the forms are advanced at a pitch of about 175 mm, the form speed along the print
path will be slightly over 100 metres per second. However, such a printing rate will
allow the printing of 36000 forms per hour, which figure is of the same order of magnitude
as the production rate of many known security printing processes where forms are printed
a number at a time on large sheets.
1. A printer arranged to print a unique sequence of characters on each of a number
of forms fed one at a time along a print path, which printer has a plurality of print
stations spaced along the print path, characterised in that each print station (19)
is adapted to print one digit on a form (11) fed along the print path whereby the
unique sequence of characters is built up by a plurality of printing operations on
the form as the form advances along the path, each print station being adapted to
print any one of a number of different characters and there being means (31,32,33,37)
arranged to permit the selective change of the printed character between each form
printing operation.
2. A printer according to claim 1, characterised in that the printer includes a further
print station at which at least one static character or group of characters is printed
on each form, which static character or group of characters remains constant for the
duration of the print run.
3. A printer according to claim 1 or claim 2, characterised in that each print station
(19) has a print roll (23) defining with a pressure roll (24) a nip through which
each form to be printed is passed, the print roll including a print head (27) carrying
a number of distinct indicia.
4. A printer according to claim 3, characterised in that each print station (19) is
arranged such that during printing of one form the print roll (23) turns through less
than one full turn, the print head (27) at any one station being advanced following
the printing of a form if the character next to be printed at that station is to be
different from the previous character.
5. A printer according to claim 4, further characterised in that the selective advance
of the print head (27) is performed by a ratchet and pawl mechanism controlled electro-mechanically.
6. A printer according to any of claims 3 to 5, characterised in that the print head
is in the form of a character wheel (27).
7. A printer according to any of claims 1 to 6, characterised in that all of the print
rolls (23) are mechanically coupled together for simultaneous synchronous rotation,
synchronised with said form feed means.
8. A printer according to any of the preceding claims, characterised in that there
is means (26) to withdraw the pressure rolls (24) out of contact with the associated
print rolls (23), in the event that no form is fed through the printer during the
operation.
9. A method of printing a number of forms so that each of which when printed carries
a unique sequence of characters, in which method a number of pre-printed forms are
provided and then fed one at a time through a printer having a plurality of print
stations, which method is characterised by the printing on each form one character
of the unique sequence at each print station, and changing the printed character at
least one print station between each form-printing operation.
10. A method according to claim 9, characterised in that the feeding of a form through
each print station (19) is synchronised to the printing operation at each station
so that the character printed at each station is aligned with and adjacent the character
printed at the immediately preceding station, whereby an aligned string of characters
is printed on the form.
11. A method according to claim 9 or claim 10, characterised in that at least one
static character or group of characters is printed on each form at a further print
station provided on the print path, which static character or group of characters
remains constant for the duration of a print run.